restructure test

- Add shard request manager

.clang-tidy

@@ -6,6 +6,7 @@ Checks: '*,
          -altera-unroll-loops,
          -android-*,
          -cert-err58-cpp,
+         -cert-str34-c,
          -cppcoreguidelines-avoid-c-arrays,
          -cppcoreguidelines-avoid-goto,
          -cppcoreguidelines-avoid-magic-numbers,
@@ -49,6 +50,7 @@ Checks: '*,
          -misc-non-private-member-variables-in-classes,
          -modernize-avoid-c-arrays,
          -modernize-concat-nested-namespaces,
+         -modernize-loop-convert,
          -modernize-pass-by-value,
          -modernize-use-equals-default,
          -modernize-use-nodiscard,

.github/workflows/diff.yaml

@@ -130,7 +130,7 @@ jobs:
           source /opt/toolchain-v4/activate
 
           # Restrict clang-tidy results only to the modified parts
-          git diff -U0 ${{ env.BASE_BRANCH }}... -- src | ./tools/github/clang-tidy/clang-tidy-diff.py -p 1 -j $THREADS -path build | tee ./build/clang_tidy_output.txt
+          git diff -U0 ${{ env.BASE_BRANCH }}... -- src | ./tools/github/clang-tidy/clang-tidy-diff.py -p 1 -j $THREADS -extra-arg="-DMG_CLANG_TIDY_CHECK" -path build | tee ./build/clang_tidy_output.txt
 
           # Fail if any warning is reported
           ! cat ./build/clang_tidy_output.txt | ./tools/github/clang-tidy/grep_error_lines.sh > /dev/null
@@ -171,7 +171,7 @@ jobs:
 
           # Run leftover CTest tests (all except unit and benchmark tests).
           cd build
-          ctest -E "(memgraph__unit|memgraph__benchmark)" --output-on-failure
+          ctest -E "(memgraph__unit|memgraph__benchmark|memgraph__simulation)" --output-on-failure
 
       - name: Run drivers tests
         run: |
@@ -262,6 +262,15 @@ jobs:
           cd build
           ctest -R memgraph__unit --output-on-failure -j$THREADS
 
+      - name: Run simulation tests
+        run: |
+          # Activate toolchain.
+          source /opt/toolchain-v4/activate
+
+          # Run unit tests.
+          cd build
+          ctest -R memgraph__simulation --output-on-failure -j$THREADS
+
       - name: Run e2e tests
         run: |
           # TODO(gitbuda): Setup mgclient and pymgclient properly.

.github/workflows/full_clang_tidy.yaml

@@ -39,7 +39,7 @@ jobs:
           source /opt/toolchain-v4/activate
 
           # The results are also written to standard output in order to retain them in the logs
-          ./tools/github/clang-tidy/run-clang-tidy.py -p build -j $THREADS -clang-tidy-binary=/opt/toolchain-v4/bin/clang-tidy "$PWD/src/*" |
+          ./tools/github/clang-tidy/run-clang-tidy.py -p build -j $THREADS -extra-arg="-DMG_CLANG_TIDY_CHECK" -clang-tidy-binary=/opt/toolchain-v4/bin/clang-tidy "$PWD/src/*" |
             tee ./build/full_clang_tidy_output.txt
 
       - name: Summarize clang-tidy results

.gitignore

@@ -23,6 +23,8 @@ cmake-build-*
 cmake/DownloadProject/
 dist/
 src/query/frontend/opencypher/generated/
+src/query/v2/frontend/opencypher/generated/
+src/parser/opencypher/generated
 tags
 ve/
 ve3/
@@ -50,15 +52,25 @@ src/distributed/pull_produce_rpc_messages.hpp
 src/distributed/storage_gc_rpc_messages.hpp
 src/distributed/token_sharing_rpc_messages.hpp
 src/distributed/updates_rpc_messages.hpp
+src/query/v2/frontend/ast/ast.hpp
 src/query/frontend/ast/ast.hpp
+src/storage/v3/bindings/ast/ast.hpp
 src/query/distributed/frontend/ast/ast_serialization.hpp
+src/query/v2/distributed/frontend/ast/ast_serialization.hpp
 src/durability/distributed/state_delta.hpp
 src/durability/single_node/state_delta.hpp
 src/durability/single_node_ha/state_delta.hpp
 src/query/frontend/semantic/symbol.hpp
+src/query/v2/frontend/semantic/symbol.hpp
+src/expr/semantic/symbol.hpp
 src/query/distributed/frontend/semantic/symbol_serialization.hpp
+src/query/v2/distributed/frontend/semantic/symbol_serialization.hpp
 src/query/distributed/plan/ops.hpp
+src/query/v2/distributed/plan/ops.hpp
 src/query/plan/operator.hpp
+src/query/v2/plan/operator.hpp
+src/parser/opencypher/generated
+src/expr/semantic/symbol.hpp
 src/raft/log_entry.hpp
 src/raft/raft_rpc_messages.hpp
 src/raft/snapshot_metadata.hpp

docs/csv-import-tool/README.md

@@ -1,204 +0,0 @@
-# CSV Import Tool Documentation
-
-CSV is a universal and very versatile data format used to store large quantities
-of data.  Each Memgraph database instance has a CSV import tool installed called
-`mg_import_csv`.  The CSV import tool should be used for initial bulk ingestion
-of data into the database.  Upon ingestion, the CSV importer creates a snapshot
-that will be used by the database to recover its state on its next startup.
-
-If you are already familiar with the Neo4j bulk import tool, then using the
-`mg_import_csv` tool should be easy.  The CSV import tool is fully compatible
-with the [Neo4j CSV
-format](https://neo4j.com/docs/operations-manual/current/tools/import/). If you
-already have a pipeline set-up for Neo4j, you should only replace `neo4j-admin
-import` with `mg_import_csv`.
-
-## CSV File Format
-
-Each row of a CSV file represents a single entry that should be imported into
-the database.  Both nodes and relationships can be imported into the database
-using CSV files.
-
-Each set of CSV files must have a header that describes the data that is stored
-in the CSV files. Each field in the CSV header is in the format
-`<name>[:<type>]` which identifies the name that should be used for that column
-and the type that should be used for that column. The type is optional and
-defaults to `string` (see the following chapter).
-
-Each CSV field must be divided using the delimiter and each CSV field can either
-be quoted or unquoted. When the field is quoted, the first and last character in
-the field *must* be the quote character. If the field isn't quoted, and a quote
-character appears in it, it is treated as a regular character. If a quote
-character appears inside a quoted string then the quote character must be
-doubled in order to escape it. Line feeds and carriage returns are ignored in
-the CSV file, also, the file can't contain a NULL character.
-
-## Properties
-
-Both nodes and relationships can have properties added to them.  When importing
-properties, the CSV importer uses the name specified in the header of the
-corresponding CSV column for the name of the property.  A property is designated
-by specifying one of the following types in the header:
- - `integer`, `int`, `long`, `byte`, `short`: creates an integer property
- - `float`, `double`: creates a float property
- - `boolean`, `bool`: creates a boolean property
- - `string`, `char`: creates a string property
-
-When importing a boolean value, the CSV field should contain exactly the text
-`true` to import a `True` boolean value.  All other text values are treated as a
-boolean value `False`.
-
-If you want to import an array of values, you can do so by appending `[]` to any
-of the above types.  The values of the array are then determined by splitting
-the raw CSV value using the array delimiter character.
-
-Assuming that the array delimiter is `;`, the following example:
-```plaintext
-first_name,last_name:string,number:integer,aliases:string[]
-John,Doe,1,Johnny;Jo;J-man
-Melissa,Doe,2,Mel
-```
-
-Will yield these results:
-```plaintext
-CREATE ({first_name: "John", last_name: "Doe", number: 1, aliases: ["Johnny", "Jo", "J-man"]});
-CREATE ({first_name: "Melissa", last_name: "Doe", number: 2, aliases: ["Mel"]});
-```
-### Nodes
-
-When importing nodes, several more types can be specified in the header of the
-CSV file (along with all property types):
- - `ID`: id of the node that should be used as the node ID when importing
-   relationships
- - `LABEL`: designates that the field contains additional labels for the node
- - `IGNORE`: designates that the field should be ignored
-
-The `ID` field type sets the internal ID that will be used for the node when
-creating relationships.  It is optional and nodes that don't have an ID value
-specified will be imported, but can't be connected to any relationships.  If you
-want to save the ID value as a property in the database, just specify a name for
-the ID (`user_id:ID`).  If you just want to use the ID during the import, leave
-out the name of the field (`:ID`).  The `ID` field also supports creating
-separate ID spaces.  The ID space is specified with the ID space name appended
-to the `ID` type in parentheses (`ID(user)`).  That allows you to have the same
-IDs (by value) for multiple different node files (for example, numbers from 1 to
-N).  The IDs in each ID space will be treated as an independent set of IDs that
-don't interfere with IDs in another ID space.
-
-The `LABEL` field type adds additional labels to the node.  The value is treated
-as an array type so that multiple additional labels can be specified for each
-node.  The value is split using the array delimiter (`--array-delimiter` flag).
-
-### Relationships
-
-In order to be able to import relationships, you must import the nodes in the
-same invocation of `mg_import_csv` that is used to import the relationships.
-
-When importing relationships, several more types can be specified in the header
-of the CSV file (along with all property types):
- - `START_ID`: id of the start node that should be connected with the
-   relationship
- - `END_ID`: id of the end node that should be connected with the relationship
- - `TYPE`: designates the type of the relationship
- - `IGNORE`: designates that the field should be ignored
-
-The `START_ID` field type sets the start node that should be connected with the
-relationship to the end node.  The field *must* be specified and the node ID
-must be one of the node IDs that were specified in the node CSV files.  The name
-of this field is ignored.  If the node ID is in an ID space, you can specify the
-ID space for the in the same way as for the node ID (`START_ID(user)`).
-
-The `END_ID` field type sets the end node that should be connected with the
-relationship to the start node.  The field *must* be specified and the node ID
-must be one of the node IDs that were specified in the node CSV files.  The name
-of this field is ignored.  If the node ID is in an ID space, you can specify the
-ID space for the in the same way as for the node ID (`END_ID(user)`).
-
-The `TYPE` field type sets the type of the relationship.  Each relationship
-*must* have a relationship type, but it doesn't necessarily need to be specified
-in the CSV file, it can also be set externally for the whole CSV file.  The name
-of this field is ignored.
-
-## CSV Importer Flags
-
-The importer has many command line options that allow you to customize the way
-the importer loads your data.
-
-The two main flags that are used to specify the input CSV files are `--nodes`
-and `--relationships`. Basic description of these flags is provided in the table
-and more detailed explainion can be found further down bellow.
-
-
-| Flag                  | Description  |
-|-----------------------| -------------- |
-|`--nodes`                | Used to specify CSV files that contain the nodes to the importer. |
-|`--relationships`        |  Used to specify CSV files that contain the relationships to the importer.|
-|`--delimiter`            | Sets the delimiter that should be used when splitting the CSV fields (default `,`)|
-|`--quote`                | Sets the quote character that should be used to quote a CSV field (default `"`)|
-|`--array-delimiter`      | Sets the delimiter that should be used when splitting array values (default `;`)|
-|`--id-type`              | Specifies which data type should be used to store the supplied <br /> node IDs when storing them as properties (if the field name is supplied). <br /> The supported values are either `STRING` or `INTEGER`. (default `STRING`)|
-|`--ignore-empty-strings` | Instructs the importer to treat all empty strings as `Null` values  <br /> instead of an empty string value (default `false`)|
-|`--ignore-extra-columns` | Instructs the importer to ignore all columns (instead of raising an error) <br /> that aren't specified after the last specified column in the CSV header. (default `false`) |
-| `--skip-bad-relationships`| Instructs the importer to ignore all relationships (instead of raising an error) <br /> that refer to nodes that don't exist in the node files. (default `false`) |
-|`--skip-duplicate-nodes`  | Instructs the importer to ignore all duplicate nodes (instead of raising an error).  <br /> Duplicate nodes are nodes that have an ID that is the same as another node that was already imported. (default `false`) |
-| `--trim-strings`| Instructs the importer to trim all of the loaded CSV field values before processing them further. <br /> Trimming the fields removes all leading and trailing whitespace from them. (default `false`) |
-
-The `--nodes` and  `--relationships` flags are used to specify CSV files that
-contain the nodes and relationships to the importer.  Multiple files can be
-specified in each supplied `--nodes` or `--relationships` flag. Files that are
-supplied in one `--nodes` or `--relationships` flag are treated by the CSV
-parser as one big CSV file.  Only the first line of the first file is parsed for
-the CSV header, all other files (and rows) are treated as data.  This is useful
-when you have a very large CSV file and don't want to edit its first line just
-to add a CSV header.  Instead, you can specify the header in a separate file
-(e.g. `users_header.csv` or `friendships_header.csv`) and have the data intact
-in the large file (e.g. `users.csv` or `friendships.csv`).  Also, you can supply
-additional labels for each set of node files.
-
-The format of `--nodes` flag is:
-`[<label>[:<label>]...=]<file>[,<file>][,<file>]...`.  Take note that only the
-first `<file>` part is mandatory, all other parts of the flag value are
-optional. Multiple `--nodes` flags can be supplied to describe multiple sets of
-different node files.  For the importer to work, at least one `--nodes` flag
-*must* be supplied.
-
-The format of `--relationships` flag is: `[<type>=]<file>[,<file>][,<file>]...`.
-Take note that only the first `<file>` part is mandatory, all other parts of the
-flag value are optional.  Multiple `--relationships` flags can be supplied to
-describe multiple sets of different relationship files.  The `--relationships`
-flag isn't mandatory.
-
-## CSV Parser Logic
-
-The CSV parser uses the same logic as the standard Python CSV parser.  The data
-is parsed in the same way as the following snippet:
-
-```python
-import csv
-for row in csv.reader(stream, strict=True):
-    # process 'row'
-```
-
-Python uses 'excel' as the default dialect when parsing CSV files and the
-default settings for the CSV parser are:
- - delimiter: `','`
- - doublequote: `True`
- - escapechar: `None`
- - lineterminator: `'\r\n'`
- - quotechar: `'"'`
- - skipinitialspace: `False`
-
-The above snippet can be expanded to:
-
-```python
-import csv
-for row in csv.reader(stream, delimiter=',', doublequote=True,
-                      escapechar=None, lineterminator='\r\n',
-                      quotechar='"', skipinitialspace=False,
-                      strict=True):
-    # process 'row'
-```
-
-For more information about the meaning of the above values, see:
-https://docs.python.org/3/library/csv.html#csv.Dialect
-

include/mg_procedure.h

@@ -1292,12 +1292,6 @@ struct mgp_proc;
 /// Describes a Memgraph magic function.
 struct mgp_func;
 
-/// All available log levels that can be used in mgp_log function
-MGP_ENUM_CLASS mgp_log_level{
-    MGP_LOG_LEVEL_TRACE, MGP_LOG_LEVEL_DEBUG, MGP_LOG_LEVEL_INFO,
-    MGP_LOG_LEVEL_WARN,  MGP_LOG_LEVEL_ERROR, MGP_LOG_LEVEL_CRITICAL,
-};
-
 /// Entry-point for a query module read procedure, invoked through openCypher.
 ///
 /// Passed in arguments will not live longer than the callback's execution.
@@ -1392,9 +1386,6 @@ enum mgp_error mgp_proc_add_result(struct mgp_proc *proc, const char *name, stru
 /// Return mgp_error::MGP_ERROR_INVALID_ARGUMENT if `name` is not a valid result name.
 /// RETURN mgp_error::MGP_ERROR_LOGIC_ERROR if a result field with the same name was already added.
 enum mgp_error mgp_proc_add_deprecated_result(struct mgp_proc *proc, const char *name, struct mgp_type *type);
-
-/// Log a message on a certain level.
-enum mgp_error mgp_log(enum mgp_log_level log_level, const char *output);
 ///@}
 
 /// @name Execution
@@ -1521,10 +1512,6 @@ enum mgp_error mgp_module_add_transformation(struct mgp_module *module, const ch
 ///
 ///@{
 
-/// State of the database that is exposed to magic functions. Currently it is unused, but it enables extending the
-/// functionalities of magic functions in future without breaking the API.
-struct mgp_func_context;
-
 /// Add a required argument to a function.
 ///
 /// The order of the added arguments corresponds to the signature of the openCypher function.

include/mgp.py

@@ -2004,82 +2004,4 @@ def _wrap_exceptions():
             setattr(module, name, wrap_function(obj))
 
 
-class Logger:
-    """Represents a Logger through which it is possible
-    to send logs via API to the graph database.
-
-    The best way to use this Logger is to have one per query module."""
-
-    __slots__ = ("_logger",)
-
-    def __init__(self):
-        self._logger = _mgp._LOGGER
-
-    def info(self, out: str) -> None:
-        """
-        Log message on INFO level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.info("Hello from query module.")```
-        """
-        self._logger.info(out)
-
-    def warning(self, out: str) -> None:
-        """
-        Log message on WARNING level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.warning("Hello from query module.")```
-        """
-        self._logger.warning(out)
-
-    def critical(self, out: str) -> None:
-        """
-        Log message on CRITICAL level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.critical("Hello from query module.")```
-        """
-        self._logger.critical(out)
-
-    def error(self, out: str) -> None:
-        """
-        Log message on ERROR level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.error("Hello from query module.")```
-        """
-        self._logger.error(out)
-
-    def trace(self, out: str) -> None:
-        """
-        Log message on TRACE level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.trace("Hello from query module.")```
-        """
-        self._logger.trace(out)
-
-    def debug(self, out: str) -> None:
-        """
-        Log message on DEBUG level..
-        Args:
-            out: String message to be logged.
-
-        Examples:
-            ```logger.debug("Hello from query module.")```
-        """
-        self._logger.debug(out)
-
-
 _wrap_exceptions()

src/CMakeLists.txt

@@ -5,16 +5,22 @@ add_subdirectory(lisp)
 add_subdirectory(utils)
 add_subdirectory(requests)
 add_subdirectory(io)
+add_subdirectory(io/simulator)
 add_subdirectory(kvstore)
 add_subdirectory(telemetry)
 add_subdirectory(communication)
 add_subdirectory(memory)
 add_subdirectory(storage/v2)
+add_subdirectory(storage/v3)
 add_subdirectory(integrations)
 add_subdirectory(query)
+add_subdirectory(query/v2)
 add_subdirectory(slk)
 add_subdirectory(rpc)
 add_subdirectory(auth)
+add_subdirectory(parser)
+add_subdirectory(expr)
+add_subdirectory(coordinator)
 
 if (MG_ENTERPRISE)
   add_subdirectory(audit)

src/auth/models.cpp

@@ -37,7 +37,7 @@ const std::vector<Permission> kPermissionsAll = {
     Permission::CONSTRAINT, Permission::DUMP,      Permission::AUTH,        Permission::REPLICATION,
     Permission::DURABILITY, Permission::READ_FILE, Permission::FREE_MEMORY, Permission::TRIGGER,
     Permission::CONFIG,     Permission::STREAM,    Permission::MODULE_READ, Permission::MODULE_WRITE,
-    Permission::WEBSOCKET};
+    Permission::WEBSOCKET,  Permission::SCHEMA};
 }  // namespace
 
 std::string PermissionToString(Permission permission) {
@@ -84,6 +84,8 @@ std::string PermissionToString(Permission permission) {
       return "MODULE_WRITE";
     case Permission::WEBSOCKET:
       return "WEBSOCKET";
+    case Permission::SCHEMA:
+      return "SCHEMA";
   }
 }
 

src/auth/models.hpp

@@ -38,7 +38,8 @@ enum class Permission : uint64_t {
   STREAM       = 1U << 17U,
   MODULE_READ  = 1U << 18U,
   MODULE_WRITE = 1U << 19U,
-  WEBSOCKET    = 1U << 20U
+  WEBSOCKET    = 1U << 20U,
+  SCHEMA       = 1U << 21U
 };
 // clang-format on
 

src/common/types.hpp

@@ -0,0 +1,19 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <cstdint>
+
+namespace memgraph::common {
+enum class SchemaType : uint8_t { BOOL, INT, STRING, DATE, LOCALTIME, LOCALDATETIME, DURATION };
+
+}  // namespace memgraph::common

src/communication/CMakeLists.txt

@@ -7,7 +7,6 @@ set(communication_src_files
     websocket/listener.cpp
     websocket/session.cpp
     bolt/v1/value.cpp
-    bolt/client.cpp
     buffer.cpp
     client.cpp
     context.cpp

src/communication/bolt/client.cpp

@@ -1,262 +0,0 @@
-// Copyright 2022 Memgraph Ltd.
-//
-// Use of this software is governed by the Business Source License
-// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
-// License, and you may not use this file except in compliance with the Business Source License.
-//
-// As of the Change Date specified in that file, in accordance with
-// the Business Source License, use of this software will be governed
-// by the Apache License, Version 2.0, included in the file
-// licenses/APL.txt.
-
-#include "communication/bolt/client.hpp"
-
-#include "communication/bolt/v1/codes.hpp"
-#include "communication/bolt/v1/value.hpp"
-#include "utils/logging.hpp"
-
-namespace {
-constexpr uint8_t kBoltV43Version[4] = {0x00, 0x00, 0x03, 0x04};
-constexpr uint8_t kEmptyBoltVersion[4] = {0x00, 0x00, 0x00, 0x00};
-}  // namespace
-namespace memgraph::communication::bolt {
-
-Client::Client(communication::ClientContext &context) : client_{&context} {}
-
-void Client::Connect(const io::network::Endpoint &endpoint, const std::string &username, const std::string &password,
-                     const std::string &client_name) {
-  if (!client_.Connect(endpoint)) {
-    throw ClientFatalException("Couldn't connect to {}!", endpoint);
-  }
-
-  if (!client_.Write(kPreamble, sizeof(kPreamble), true)) {
-    spdlog::error("Couldn't send preamble!");
-    throw ServerCommunicationException();
-  }
-
-  if (!client_.Write(kBoltV43Version, sizeof(kBoltV43Version), true)) {
-    spdlog::error("Couldn't send protocol version!");
-    throw ServerCommunicationException();
-  }
-
-  for (int i = 0; i < 3; ++i) {
-    if (!client_.Write(kEmptyBoltVersion, sizeof(kEmptyBoltVersion), i != 2)) {
-      spdlog::error("Couldn't send protocol version!");
-      throw ServerCommunicationException();
-    }
-  }
-
-  if (!client_.Read(sizeof(kBoltV43Version))) {
-    spdlog::error("Couldn't get negotiated protocol version!");
-    throw ServerCommunicationException();
-  }
-
-  if (memcmp(kBoltV43Version, client_.GetData(), sizeof(kBoltV43Version)) != 0) {
-    spdlog::error("Server negotiated unsupported protocol version!");
-    throw ClientFatalException("The server negotiated an usupported protocol version!");
-  }
-  client_.ShiftData(sizeof(kBoltV43Version));
-
-  if (!encoder_.MessageInit({{"user_agent", client_name},
-                             {"scheme", "basic"},
-                             {"principal", username},
-                             {"credentials", password},
-                             {"routing", {}}})) {
-    spdlog::error("Couldn't send init message!");
-    throw ServerCommunicationException();
-  }
-
-  Signature signature{};
-  Value metadata;
-  if (!ReadMessage(signature, metadata)) {
-    spdlog::error("Couldn't read init message response!");
-    throw ServerCommunicationException();
-  }
-  if (signature != Signature::Success) {
-    spdlog::error("Handshake failed!");
-    throw ClientFatalException("Handshake with the server failed!");
-  }
-
-  spdlog::debug("Metadata of init message response: {}", metadata);
-}
-
-QueryData Client::Execute(const std::string &query, const std::map<std::string, Value> &parameters) {
-  if (!client_.IsConnected()) {
-    throw ClientFatalException("You must first connect to the server before using the client!");
-  }
-
-  spdlog::debug("Sending run message with statement: '{}'; parameters: {}", query, parameters);
-
-  // It is super critical from performance point of view to send the pull message right after the run message. Otherwise
-  // the performance will degrade multiple magnitudes.
-  encoder_.MessageRun(query, parameters, {});
-  encoder_.MessagePull({});
-
-  spdlog::debug("Reading run message response");
-  Signature signature{};
-  Value fields;
-  if (!ReadMessage(signature, fields)) {
-    throw ServerCommunicationException();
-  }
-  if (fields.type() != Value::Type::Map) {
-    throw ServerMalformedDataException();
-  }
-
-  if (signature == Signature::Failure) {
-    HandleFailure<ClientQueryException>(fields.ValueMap());
-  }
-  if (signature != Signature::Success) {
-    throw ServerMalformedDataException();
-  }
-
-  spdlog::debug("Reading pull_all message response");
-  Marker marker{};
-  Value metadata;
-  std::vector<std::vector<Value>> records;
-  while (true) {
-    if (!GetMessage()) {
-      throw ServerCommunicationException();
-    }
-    if (!decoder_.ReadMessageHeader(&signature, &marker)) {
-      throw ServerCommunicationException();
-    }
-    if (signature == Signature::Record) {
-      Value record;
-      if (!decoder_.ReadValue(&record, Value::Type::List)) {
-        throw ServerCommunicationException();
-      }
-      records.emplace_back(std::move(record.ValueList()));
-    } else if (signature == Signature::Success) {
-      if (!decoder_.ReadValue(&metadata)) {
-        throw ServerCommunicationException();
-      }
-      break;
-    } else if (signature == Signature::Failure) {
-      Value data;
-      if (!decoder_.ReadValue(&data)) {
-        throw ServerCommunicationException();
-      }
-      HandleFailure<ClientQueryException>(data.ValueMap());
-    } else {
-      throw ServerMalformedDataException();
-    }
-  }
-
-  if (metadata.type() != Value::Type::Map) {
-    throw ServerMalformedDataException();
-  }
-
-  QueryData ret{{}, std::move(records), std::move(metadata.ValueMap())};
-
-  auto &header = fields.ValueMap();
-  if (header.find("fields") == header.end()) {
-    throw ServerMalformedDataException();
-  }
-  if (header["fields"].type() != Value::Type::List) {
-    throw ServerMalformedDataException();
-  }
-  auto &field_vector = header["fields"].ValueList();
-
-  for (auto &field_item : field_vector) {
-    if (field_item.type() != Value::Type::String) {
-      throw ServerMalformedDataException();
-    }
-    ret.fields.emplace_back(std::move(field_item.ValueString()));
-  }
-
-  return ret;
-}
-
-void Client::Reset() {
-  if (!client_.IsConnected()) {
-    throw ClientFatalException("You must first connect to the server before using the client!");
-  }
-
-  spdlog::debug("Sending reset message");
-
-  encoder_.MessageReset();
-
-  Signature signature{};
-  Value fields;
-  // In Execute the pull message is sent right after the run message without reading the answer for the run message.
-  // That means some of the messages sent might get ignored.
-  while (true) {
-    if (!ReadMessage(signature, fields)) {
-      throw ServerCommunicationException();
-    }
-    if (signature == Signature::Success) {
-      break;
-    }
-    if (signature != Signature::Ignored) {
-      throw ServerMalformedDataException();
-    }
-  }
-}
-
-std::optional<std::map<std::string, Value>> Client::Route(const std::map<std::string, Value> &routing,
-                                                          const std::vector<Value> &bookmarks,
-                                                          const std::optional<std::string> &db) {
-  if (!client_.IsConnected()) {
-    throw ClientFatalException("You must first connect to the server before using the client!");
-  }
-
-  spdlog::debug("Sending route message with routing: {}; bookmarks: {}; db: {}", routing, bookmarks,
-                db.has_value() ? *db : Value());
-
-  encoder_.MessageRoute(routing, bookmarks, db);
-
-  spdlog::debug("Reading route message response");
-  Signature signature{};
-  Value fields;
-  if (!ReadMessage(signature, fields)) {
-    throw ServerCommunicationException();
-  }
-  if (signature == Signature::Ignored) {
-    return std::nullopt;
-  }
-  if (signature == Signature::Failure) {
-    HandleFailure(fields.ValueMap());
-  }
-  if (signature != Signature::Success) {
-    throw ServerMalformedDataException{};
-  }
-  return fields.ValueMap();
-}
-
-void Client::Close() { client_.Close(); };
-
-bool Client::GetMessage() {
-  client_.ClearData();
-  while (true) {
-    if (!client_.Read(kChunkHeaderSize)) return false;
-
-    size_t chunk_size = client_.GetData()[0];
-    chunk_size <<= 8U;
-    chunk_size += client_.GetData()[1];
-    if (chunk_size == 0) return true;
-
-    if (!client_.Read(chunk_size)) return false;
-    if (decoder_buffer_.GetChunk() != ChunkState::Whole) return false;
-    client_.ClearData();
-  }
-  return true;
-}
-
-bool Client::ReadMessage(Signature &signature, Value &ret) {
-  Marker marker{};
-  if (!GetMessage()) return false;
-  if (!decoder_.ReadMessageHeader(&signature, &marker)) return false;
-  return ReadMessageData(marker, ret);
-}
-
-bool Client::ReadMessageData(Marker marker, Value &ret) {
-  if (marker == Marker::TinyStruct) {
-    ret = Value();
-    return true;
-  }
-  if (marker == Marker::TinyStruct1) {
-    return decoder_.ReadValue(&ret);
-  }
-  return false;
-}
-}  // namespace memgraph::communication::bolt

src/communication/bolt/client.hpp

@@ -11,12 +11,6 @@
 
 #pragma once
 
-#include <map>
-#include <optional>
-#include <string>
-#include <vector>
-
-#include "communication/bolt/v1/codes.hpp"
 #include "communication/bolt/v1/decoder/chunked_decoder_buffer.hpp"
 #include "communication/bolt/v1/decoder/decoder.hpp"
 #include "communication/bolt/v1/encoder/chunked_encoder_buffer.hpp"
@@ -25,17 +19,22 @@
 #include "communication/context.hpp"
 #include "io/network/endpoint.hpp"
 #include "utils/exceptions.hpp"
+#include "utils/logging.hpp"
 
 namespace memgraph::communication::bolt {
 
-class FailureResponseException : public utils::BasicException {
+/// This exception is thrown whenever an error occurs during query execution
+/// that isn't fatal (eg. mistyped query or some transient error occurred).
+/// It should be handled by everyone who uses the client.
+class ClientQueryException : public utils::BasicException {
  public:
-  FailureResponseException() : utils::BasicException{"Couldn't execute query!"} {}
+  using utils::BasicException::BasicException;
 
-  explicit FailureResponseException(const std::string &message) : utils::BasicException{message} {}
+  ClientQueryException() : utils::BasicException("Couldn't execute query!") {}
 
-  FailureResponseException(const std::string &code, const std::string &message)
-      : utils::BasicException{message}, code_{code} {}
+  template <class... Args>
+  ClientQueryException(const std::string &code, Args &&...args)
+      : utils::BasicException(std::forward<Args>(args)...), code_(code) {}
 
   const std::string &code() const { return code_; }
 
@@ -43,14 +42,6 @@ class FailureResponseException : public utils::BasicException {
   std::string code_;
 };
 
-/// This exception is thrown whenever an error occurs during query execution
-/// that isn't fatal (eg. mistyped query or some transient error occurred).
-/// It should be handled by everyone who uses the client.
-class ClientQueryException : public FailureResponseException {
- public:
-  using FailureResponseException::FailureResponseException;
-};
-
 /// This exception is thrown whenever a fatal error occurs during query
 /// execution and/or connecting to the server.
 /// It should be handled by everyone who uses the client.
@@ -85,13 +76,12 @@ struct QueryData {
 /// server. It supports both SSL and plaintext connections.
 class Client final {
  public:
-  explicit Client(communication::ClientContext &context);
+  explicit Client(communication::ClientContext *context) : client_(context) {}
 
   Client(const Client &) = delete;
   Client(Client &&) = delete;
   Client &operator=(const Client &) = delete;
   Client &operator=(Client &&) = delete;
-  ~Client() = default;
 
   /// Method used to connect to the server. Before executing queries this method
   /// should be called to set-up the connection to the server. After the
@@ -99,7 +89,50 @@ class Client final {
   /// established connection.
   /// @throws ClientFatalException when we couldn't connect to the server
   void Connect(const io::network::Endpoint &endpoint, const std::string &username, const std::string &password,
-               const std::string &client_name = "memgraph-bolt");
+               const std::string &client_name = "memgraph-bolt") {
+    if (!client_.Connect(endpoint)) {
+      throw ClientFatalException("Couldn't connect to {}!", endpoint);
+    }
+
+    if (!client_.Write(kPreamble, sizeof(kPreamble), true)) {
+      SPDLOG_ERROR("Couldn't send preamble!");
+      throw ServerCommunicationException();
+    }
+    for (int i = 0; i < 4; ++i) {
+      if (!client_.Write(kProtocol, sizeof(kProtocol), i != 3)) {
+        SPDLOG_ERROR("Couldn't send protocol version!");
+        throw ServerCommunicationException();
+      }
+    }
+
+    if (!client_.Read(sizeof(kProtocol))) {
+      SPDLOG_ERROR("Couldn't get negotiated protocol version!");
+      throw ServerCommunicationException();
+    }
+    if (memcmp(kProtocol, client_.GetData(), sizeof(kProtocol)) != 0) {
+      SPDLOG_ERROR("Server negotiated unsupported protocol version!");
+      throw ClientFatalException("The server negotiated an usupported protocol version!");
+    }
+    client_.ShiftData(sizeof(kProtocol));
+
+    if (!encoder_.MessageInit(client_name, {{"scheme", "basic"}, {"principal", username}, {"credentials", password}})) {
+      SPDLOG_ERROR("Couldn't send init message!");
+      throw ServerCommunicationException();
+    }
+
+    Signature signature;
+    Value metadata;
+    if (!ReadMessage(&signature, &metadata)) {
+      SPDLOG_ERROR("Couldn't read init message response!");
+      throw ServerCommunicationException();
+    }
+    if (signature != Signature::Success) {
+      SPDLOG_ERROR("Handshake failed!");
+      throw ClientFatalException("Handshake with the server failed!");
+    }
+
+    SPDLOG_INFO("Metadata of init message response: {}", metadata);
+  }
 
   /// Function used to execute queries against the server. Before you can
   /// execute queries you must connect the client to the server.
@@ -107,40 +140,167 @@ class Client final {
   ///                              executing the query (eg. mistyped query,
   ///                              etc.)
   /// @throws ClientFatalException when we couldn't communicate with the server
-  QueryData Execute(const std::string &query, const std::map<std::string, Value> &parameters);
-
-  /// Close the active client connection.
-  void Close();
-
-  /// Can be used to reset the active client connection. Reset is automatically sent after receiving a failure message
-  /// from the server, which result in throwing an FailureResponseException or any exception derived from it.
-  void Reset();
-
-  /// Can be used to send a route message.
-  std::optional<std::map<std::string, Value>> Route(const std::map<std::string, Value> &routing,
-                                                    const std::vector<Value> &bookmarks,
-                                                    const std::optional<std::string> &db);
-
- private:
-  using ClientEncoder = ClientEncoder<ChunkedEncoderBuffer<communication::ClientOutputStream>>;
-
-  template <typename TException = FailureResponseException>
-  [[noreturn]] void HandleFailure(const std::map<std::string, Value> &response_map) {
-    Reset();
-    auto it = response_map.find("message");
-    if (it != response_map.end()) {
-      auto it_code = response_map.find("code");
-      if (it_code != response_map.end()) {
-        throw TException(it_code->second.ValueString(), it->second.ValueString());
-      }
-      throw TException("", it->second.ValueString());
+  QueryData Execute(const std::string &query, const std::map<std::string, Value> &parameters) {
+    if (!client_.IsConnected()) {
+      throw ClientFatalException("You must first connect to the server before using the client!");
     }
-    throw TException();
+
+    SPDLOG_INFO("Sending run message with statement: '{}'; parameters: {}", query, parameters);
+
+    encoder_.MessageRun(query, parameters);
+    encoder_.MessagePullAll();
+
+    SPDLOG_INFO("Reading run message response");
+    Signature signature;
+    Value fields;
+    if (!ReadMessage(&signature, &fields)) {
+      throw ServerCommunicationException();
+    }
+    if (fields.type() != Value::Type::Map) {
+      throw ServerMalformedDataException();
+    }
+
+    if (signature == Signature::Failure) {
+      HandleFailure();
+      auto &tmp = fields.ValueMap();
+      auto it = tmp.find("message");
+      if (it != tmp.end()) {
+        auto it_code = tmp.find("code");
+        if (it_code != tmp.end()) {
+          throw ClientQueryException(it_code->second.ValueString(), it->second.ValueString());
+        } else {
+          throw ClientQueryException("", it->second.ValueString());
+        }
+      }
+      throw ClientQueryException();
+    } else if (signature != Signature::Success) {
+      throw ServerMalformedDataException();
+    }
+
+    SPDLOG_INFO("Reading pull_all message response");
+    Marker marker;
+    Value metadata;
+    std::vector<std::vector<Value>> records;
+    while (true) {
+      if (!GetMessage()) {
+        throw ServerCommunicationException();
+      }
+      if (!decoder_.ReadMessageHeader(&signature, &marker)) {
+        throw ServerCommunicationException();
+      }
+      if (signature == Signature::Record) {
+        Value record;
+        if (!decoder_.ReadValue(&record, Value::Type::List)) {
+          throw ServerCommunicationException();
+        }
+        records.emplace_back(std::move(record.ValueList()));
+      } else if (signature == Signature::Success) {
+        if (!decoder_.ReadValue(&metadata)) {
+          throw ServerCommunicationException();
+        }
+        break;
+      } else if (signature == Signature::Failure) {
+        Value data;
+        if (!decoder_.ReadValue(&data)) {
+          throw ServerCommunicationException();
+        }
+        HandleFailure();
+        auto &tmp = data.ValueMap();
+        auto it = tmp.find("message");
+        if (it != tmp.end()) {
+          auto it_code = tmp.find("code");
+          if (it_code != tmp.end()) {
+            throw ClientQueryException(it_code->second.ValueString(), it->second.ValueString());
+          } else {
+            throw ClientQueryException("", it->second.ValueString());
+          }
+        }
+        throw ClientQueryException();
+      } else {
+        throw ServerMalformedDataException();
+      }
+    }
+
+    if (metadata.type() != Value::Type::Map) {
+      throw ServerMalformedDataException();
+    }
+
+    QueryData ret{{}, std::move(records), std::move(metadata.ValueMap())};
+
+    auto &header = fields.ValueMap();
+    if (header.find("fields") == header.end()) {
+      throw ServerMalformedDataException();
+    }
+    if (header["fields"].type() != Value::Type::List) {
+      throw ServerMalformedDataException();
+    }
+    auto &field_vector = header["fields"].ValueList();
+
+    for (auto &field_item : field_vector) {
+      if (field_item.type() != Value::Type::String) {
+        throw ServerMalformedDataException();
+      }
+      ret.fields.emplace_back(std::move(field_item.ValueString()));
+    }
+
+    return ret;
   }
 
-  bool GetMessage();
-  bool ReadMessage(Signature &signature, Value &ret);
-  bool ReadMessageData(Marker marker, Value &ret);
+  /// Close the active client connection.
+  void Close() { client_.Close(); };
+
+ private:
+  bool GetMessage() {
+    client_.ClearData();
+    while (true) {
+      if (!client_.Read(kChunkHeaderSize)) return false;
+
+      size_t chunk_size = client_.GetData()[0];
+      chunk_size <<= 8;
+      chunk_size += client_.GetData()[1];
+      if (chunk_size == 0) return true;
+
+      if (!client_.Read(chunk_size)) return false;
+      if (decoder_buffer_.GetChunk() != ChunkState::Whole) return false;
+      client_.ClearData();
+    }
+    return true;
+  }
+
+  bool ReadMessage(Signature *signature, Value *ret) {
+    Marker marker;
+    if (!GetMessage()) return false;
+    if (!decoder_.ReadMessageHeader(signature, &marker)) return false;
+    return ReadMessageData(marker, ret);
+  }
+
+  bool ReadMessageData(Marker marker, Value *ret) {
+    if (marker == Marker::TinyStruct) {
+      *ret = Value();
+      return true;
+    } else if (marker == Marker::TinyStruct1) {
+      return decoder_.ReadValue(ret);
+    }
+    return false;
+  }
+
+  void HandleFailure() {
+    if (!encoder_.MessageAckFailure()) {
+      throw ServerCommunicationException();
+    }
+    while (true) {
+      Signature signature;
+      Value data;
+      if (!ReadMessage(&signature, &data)) {
+        throw ServerCommunicationException();
+      }
+      if (signature == Signature::Success) {
+        break;
+      } else if (signature != Signature::Ignored) {
+        throw ServerMalformedDataException();
+      }
+    }
+  }
 
   // client
   communication::Client client_;
@@ -153,6 +313,6 @@ class Client final {
 
   // encoder objects
   ChunkedEncoderBuffer<communication::ClientOutputStream> encoder_buffer_{output_stream_};
-  ClientEncoder encoder_{encoder_buffer_};
+  ClientEncoder<ChunkedEncoderBuffer<communication::ClientOutputStream>> encoder_{encoder_buffer_};
 };
 }  // namespace memgraph::communication::bolt

src/communication/bolt/v1/codes.hpp

@@ -16,6 +16,7 @@
 namespace memgraph::communication::bolt {
 
 inline constexpr uint8_t kPreamble[4] = {0x60, 0x60, 0xB0, 0x17};
+inline constexpr uint8_t kProtocol[4] = {0x00, 0x00, 0x00, 0x01};
 
 enum class Signature : uint8_t {
   Noop = 0x00,

src/communication/bolt/v1/encoder/client_encoder.hpp

@@ -11,11 +11,6 @@
 
 #pragma once
 
-#include <map>
-#include <optional>
-#include <string>
-#include <vector>
-
 #include "communication/bolt/v1/codes.hpp"
 #include "communication/bolt/v1/encoder/base_encoder.hpp"
 
@@ -35,7 +30,6 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   using BaseEncoder<Buffer>::WriteList;
   using BaseEncoder<Buffer>::WriteMap;
   using BaseEncoder<Buffer>::WriteString;
-  using BaseEncoder<Buffer>::WriteNull;
   using BaseEncoder<Buffer>::buffer_;
 
  public:
@@ -44,9 +38,10 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   /**
    * Writes a Init message.
    *
-   * From the Bolt v4.3 documentation:
-   *   HelloMess (signature=0x01) {
-   *     Map<String,Value> extra
+   * From the Bolt v1 documentation:
+   *   InitMessage (signature=0x01) {
+   *     String clientName
+   *     Map<String,Value> authToken
    *   }
    *
    * @param client_name the name of the connected client
@@ -54,10 +49,11 @@ class ClientEncoder : private BaseEncoder<Buffer> {
    * @returns true if the data was successfully sent to the client
    *          when flushing, false otherwise
    */
-  bool MessageInit(const std::map<std::string, Value> &extra) {
-    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct1));
+  bool MessageInit(const std::string client_name, const std::map<std::string, Value> &auth_token) {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct2));
     WriteRAW(utils::UnderlyingCast(Signature::Init));
-    WriteMap(extra);
+    WriteString(client_name);
+    WriteMap(auth_token);
     // Try to flush all remaining data in the buffer, but tell it that we will
     // send more data (the end of message chunk).
     if (!buffer_.Flush(true)) return false;
@@ -68,11 +64,10 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   /**
    * Writes a Run message.
    *
-   * From the Bolt v4.3 documentation:
+   * From the Bolt v1 documentation:
    *   RunMessage (signature=0x10) {
-   *     String            statement
-   *     Map<String,Value> parameters
-   *     Map<String,Value> extra
+   *     String             statement
+   *     Map<String,Value>  parameters
    *   }
    *
    * @param statement the statement that should be executed
@@ -80,13 +75,11 @@ class ClientEncoder : private BaseEncoder<Buffer> {
    * @returns true if the data was successfully sent to the client
    *          when flushing, false otherwise
    */
-  bool MessageRun(const std::string &statement, const std::map<std::string, Value> &parameters,
-                  const std::map<std::string, Value> &extra, bool have_more = true) {
-    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct3));
+  bool MessageRun(const std::string &statement, const std::map<std::string, Value> &parameters, bool have_more = true) {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct2));
     WriteRAW(utils::UnderlyingCast(Signature::Run));
     WriteString(statement);
     WriteMap(parameters);
-    WriteMap(extra);
     // Try to flush all remaining data in the buffer, but tell it that we will
     // send more data (the end of message chunk).
     if (!buffer_.Flush(true)) return false;
@@ -97,20 +90,18 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   }
 
   /**
-   * Writes a Discard message.
+   * Writes a DiscardAll message.
    *
-   * From the Bolt v4.3 documentation:
+   * From the Bolt v1 documentation:
    *   DiscardMessage (signature=0x2F) {
-   *     Map<String,Value> extra
    *   }
    *
    * @returns true if the data was successfully sent to the client
    *          when flushing, false otherwise
    */
-  bool MessageDiscard(const std::map<std::string, Value> &extra) {
-    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct1));
+  bool MessageDiscardAll() {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct));
     WriteRAW(utils::UnderlyingCast(Signature::Discard));
-    WriteMap(extra);
     // Try to flush all remaining data in the buffer, but tell it that we will
     // send more data (the end of message chunk).
     if (!buffer_.Flush(true)) return false;
@@ -121,18 +112,36 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   /**
    * Writes a PullAll message.
    *
-   * From the Bolt v4.3 documentation:
-   *   PullMessage (signature=0x3F) {
-   *     Map<String,Value> extra
+   * From the Bolt v1 documentation:
+   *   PullAllMessage (signature=0x3F) {
    *   }
    *
    * @returns true if the data was successfully sent to the client
    *          when flushing, false otherwise
    */
-  bool MessagePull(const std::map<std::string, Value> &extra) {
-    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct1));
+  bool MessagePullAll() {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct));
     WriteRAW(utils::UnderlyingCast(Signature::Pull));
-    WriteMap(extra);
+    // Try to flush all remaining data in the buffer, but tell it that we will
+    // send more data (the end of message chunk).
+    if (!buffer_.Flush(true)) return false;
+    // Flush an empty chunk to indicate that the message is done.
+    return buffer_.Flush();
+  }
+
+  /**
+   * Writes a AckFailure message.
+   *
+   * From the Bolt v1 documentation:
+   *   AckFailureMessage (signature=0x0E) {
+   *   }
+   *
+   * @returns true if the data was successfully sent to the client
+   *          when flushing, false otherwise
+   */
+  bool MessageAckFailure() {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct));
+    WriteRAW(utils::UnderlyingCast(Signature::AckFailure));
     // Try to flush all remaining data in the buffer, but tell it that we will
     // send more data (the end of message chunk).
     if (!buffer_.Flush(true)) return false;
@@ -143,7 +152,7 @@ class ClientEncoder : private BaseEncoder<Buffer> {
   /**
    * Writes a Reset message.
    *
-   * From the Bolt v4.3 documentation:
+   * From the Bolt v1 documentation:
    *   ResetMessage (signature=0x0F) {
    *   }
    *
@@ -159,36 +168,5 @@ class ClientEncoder : private BaseEncoder<Buffer> {
     // Flush an empty chunk to indicate that the message is done.
     return buffer_.Flush();
   }
-
-  /**
-   * Writes a Route message.
-   *
-   * From the Bolt v4.3 documentation:
-   *   RouteMessage (signature=0x0F) {
-   *     Map<String,Value> routing
-   *     List<String>      bookmarks
-   *     String            db
-   *   }
-   *
-   * @returns true if the data was successfully sent to the client
-   *          when flushing, false otherwise
-   */
-  bool MessageRoute(const std::map<std::string, Value> &routing, const std::vector<Value> &bookmarks,
-                    const std::optional<std::string> &db) {
-    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct3));
-    WriteRAW(utils::UnderlyingCast(Signature::Route));
-    WriteMap(routing);
-    WriteList(bookmarks);
-    if (db.has_value()) {
-      WriteString(*db);
-    } else {
-      WriteNull();
-    }
-    // Try to flush all remaining data in the buffer, but tell it that we will
-    // send more data (the end of message chunk).
-    if (!buffer_.Flush(true)) return false;
-    // Flush an empty chunk to indicate that the message is done.
-    return buffer_.Flush();
-  }
 };
 }  // namespace memgraph::communication::bolt

src/communication/bolt/v1/encoder/encoder.hpp

@@ -117,6 +117,29 @@ class Encoder : private BaseEncoder<Buffer> {
     return buffer_.Flush();
   }
 
+  /**
+   * Sends an Ignored message.
+   *
+   * From the bolt v1 documentation:
+   *   IgnoredMessage (signature=0x7E) {
+   *     Map<String,Value> metadata
+   *   }
+   *
+   * @param metadata the metadata map object that should be sent
+   * @returns true if the data was successfully sent to the client,
+   *          false otherwise
+   */
+  bool MessageIgnored(const std::map<std::string, Value> &metadata) {
+    WriteRAW(utils::UnderlyingCast(Marker::TinyStruct1));
+    WriteRAW(utils::UnderlyingCast(Signature::Ignored));
+    WriteMap(metadata);
+    // Try to flush all remaining data in the buffer, but tell it that we will
+    // send more data (the end of message chunk).
+    if (!buffer_.Flush(true)) return false;
+    // Flush an empty chunk to indicate that the message is done.
+    return buffer_.Flush();
+  }
+
   /**
    * Sends an Ignored message.
    *

src/communication/bolt/v1/states/error.hpp

@@ -15,7 +15,6 @@
 
 #include "communication/bolt/v1/codes.hpp"
 #include "communication/bolt/v1/state.hpp"
-#include "communication/bolt/v1/states/handlers.hpp"
 #include "communication/bolt/v1/value.hpp"
 #include "utils/cast.hpp"
 #include "utils/likely.hpp"
@@ -31,8 +30,8 @@ namespace memgraph::communication::bolt {
  */
 template <typename TSession>
 State StateErrorRun(TSession &session, State state) {
-  Marker marker{};
-  Signature signature{};
+  Marker marker;
+  Signature signature;
   if (!session.decoder_.ReadMessageHeader(&signature, &marker)) {
     spdlog::trace("Missing header data!");
     return State::Close;
@@ -46,49 +45,54 @@ State StateErrorRun(TSession &session, State state) {
   // Clear the data buffer if it has any leftover data.
   session.encoder_buffer_.Clear();
 
-  if (session.version_.major == 1 && signature == Signature::AckFailure) {
-    spdlog::trace("AckFailure received");
+  if ((session.version_.major == 1 && signature == Signature::AckFailure) || signature == Signature::Reset) {
+    if (signature == Signature::AckFailure) {
+      spdlog::trace("AckFailure received");
+    } else {
+      spdlog::trace("Reset received");
+    }
 
     if (!session.encoder_.MessageSuccess()) {
       spdlog::trace("Couldn't send success message!");
       return State::Close;
     }
 
+    if (signature == Signature::Reset) {
+      session.Abort();
+      return State::Idle;
+    }
+
     // We got AckFailure get back to right state.
     MG_ASSERT(state == State::Error, "Shouldn't happen");
     return State::Idle;
-  }
-  if (signature == Signature::Reset) {
-    spdlog::trace("Reset received");
-    return HandleReset(session, marker);
-  }
+  } else {
+    uint8_t value = utils::UnderlyingCast(marker);
 
-  uint8_t value = utils::UnderlyingCast(marker);
-
-  // All bolt client messages have less than 15 parameters so if we receive
-  // anything than a TinyStruct it's an error.
-  if ((value & 0xF0U) != utils::UnderlyingCast(Marker::TinyStruct)) {
-    spdlog::trace("Expected TinyStruct marker, but received 0x{:02X}!", value);
-    return State::Close;
-  }
-
-  // We need to clean up all parameters from this command.
-  value &= 0x0FU;  // The length is stored in the lower nibble.
-  Value dv;
-  for (int i = 0; i < value; ++i) {
-    if (!session.decoder_.ReadValue(&dv)) {
-      spdlog::trace("Couldn't clean up parameter {} / {}!", i, value);
+    // All bolt client messages have less than 15 parameters so if we receive
+    // anything than a TinyStruct it's an error.
+    if ((value & 0xF0) != utils::UnderlyingCast(Marker::TinyStruct)) {
+      spdlog::trace("Expected TinyStruct marker, but received 0x{:02X}!", value);
       return State::Close;
     }
-  }
 
-  // Ignore this message.
-  if (!session.encoder_.MessageIgnored()) {
-    spdlog::trace("Couldn't send ignored message!");
-    return State::Close;
-  }
+    // We need to clean up all parameters from this command.
+    value &= 0x0F;  // The length is stored in the lower nibble.
+    Value dv;
+    for (int i = 0; i < value; ++i) {
+      if (!session.decoder_.ReadValue(&dv)) {
+        spdlog::trace("Couldn't clean up parameter {} / {}!", i, value);
+        return State::Close;
+      }
+    }
 
-  // Cleanup done, command ignored, stay in error state.
-  return state;
+    // Ignore this message.
+    if (!session.encoder_.MessageIgnored()) {
+      spdlog::trace("Couldn't send ignored message!");
+      return State::Close;
+    }
+
+    // Cleanup done, command ignored, stay in error state.
+    return state;
+  }
 }
 }  // namespace memgraph::communication::bolt

src/communication/bolt/v1/states/executing.hpp

@@ -74,7 +74,7 @@ State RunHandlerV4(Signature signature, TSession &session, State state, Marker m
     }
     case Signature::Route: {
       if constexpr (bolt_minor >= 3) {
-        if (signature == Signature::Route) return HandleRoute<TSession>(session, marker);
+        if (signature == Signature::Route) return HandleRoute<TSession>(session);
       } else {
         spdlog::trace("Supported only in bolt v4.3");
         return State::Close;

src/communication/bolt/v1/states/handlers.hpp

@@ -18,7 +18,6 @@
 
 #include "communication/bolt/v1/codes.hpp"
 #include "communication/bolt/v1/constants.hpp"
-#include "communication/bolt/v1/exceptions.hpp"
 #include "communication/bolt/v1/state.hpp"
 #include "communication/bolt/v1/value.hpp"
 #include "communication/exceptions.hpp"
@@ -137,7 +136,7 @@ template <bool is_pull, typename TSession>
 State HandlePullDiscardV1(TSession &session, const State state, const Marker marker) {
   const auto expected_marker = Marker::TinyStruct;
   if (marker != expected_marker) {
-    spdlog::trace("Expected TinyStruct marker, but received 0x{:02X}!", utils::UnderlyingCast(marker));
+    spdlog::trace("Expected {} marker, but received 0x{:02X}!", "TinyStruct", utils::UnderlyingCast(marker));
     return State::Close;
   }
 
@@ -158,7 +157,7 @@ template <bool is_pull, typename TSession>
 State HandlePullDiscardV4(TSession &session, const State state, const Marker marker) {
   const auto expected_marker = Marker::TinyStruct1;
   if (marker != expected_marker) {
-    spdlog::trace("Expected TinyStruct1 marker, but received 0x{:02X}!", utils::UnderlyingCast(marker));
+    spdlog::trace("Expected {} marker, but received 0x{:02X}!", "TinyStruct1", utils::UnderlyingCast(marker));
     return State::Close;
   }
 
@@ -217,8 +216,7 @@ State HandleRunV1(TSession &session, const State state, const Marker marker) {
                   session.version_.major == 1 ? "TinyStruct2" : "TinyStruct3", utils::UnderlyingCast(marker));
     return State::Close;
   }
-  Value query;
-  Value params;
+  Value query, params;
   if (!session.decoder_.ReadValue(&query, Value::Type::String)) {
     spdlog::trace("Couldn't read query string!");
     return State::Close;
@@ -236,12 +234,10 @@ template <typename TSession>
 State HandleRunV4(TSession &session, const State state, const Marker marker) {
   const auto expected_marker = Marker::TinyStruct3;
   if (marker != expected_marker) {
-    spdlog::trace("Expected TinyStruct3 marker, but received 0x{:02X}!", utils::UnderlyingCast(marker));
+    spdlog::trace("Expected {} marker, but received 0x{:02X}!", "TinyStruct3", utils::UnderlyingCast(marker));
     return State::Close;
   }
-  Value query;
-  Value params;
-  Value extra;
+  Value query, params, extra;
   if (!session.decoder_.ReadValue(&query, Value::Type::String)) {
     spdlog::trace("Couldn't read query string!");
     return State::Close;
@@ -296,6 +292,9 @@ State HandleReset(TSession &session, const Marker marker) {
     return State::Close;
   }
 
+  // Clear all pending data and send a success message.
+  session.encoder_buffer_.Clear();
+
   if (!session.encoder_.MessageSuccess()) {
     spdlog::trace("Couldn't send success message!");
     return State::Close;
@@ -404,33 +403,12 @@ State HandleGoodbye() {
 }
 
 template <typename TSession>
-State HandleRoute(TSession &session, const Marker marker) {
-  // Route message is not implemented since it is Neo4j specific, therefore we will receive it and inform user that
-  // there is no implementation. Before that, we have to read out the fields from the buffer to leave it in a clean
-  // state.
-  if (marker != Marker::TinyStruct3) {
-    spdlog::trace("Expected TinyStruct3 marker, but received 0x{:02x}!", utils::UnderlyingCast(marker));
-    return State::Close;
-  }
-  Value routing;
-  if (!session.decoder_.ReadValue(&routing, Value::Type::Map)) {
-    spdlog::trace("Couldn't read routing field!");
-    return State::Close;
-  }
-
-  Value bookmarks;
-  if (!session.decoder_.ReadValue(&bookmarks, Value::Type::List)) {
-    spdlog::trace("Couldn't read bookmarks field!");
-    return State::Close;
-  }
-  Value db;
-  if (!session.decoder_.ReadValue(&db)) {
-    spdlog::trace("Couldn't read db field!");
-    return State::Close;
-  }
+State HandleRoute(TSession &session) {
+  // Route message is not implemented since it is neo4j specific, therefore we
+  // will receive it an inform user that there is no implementation.
   session.encoder_buffer_.Clear();
   bool fail_sent =
-      session.encoder_.MessageFailure({{"code", "66"}, {"message", "Route message is not supported in Memgraph!"}});
+      session.encoder_.MessageFailure({{"code", 66}, {"message", "Route message not supported in Memgraph!"}});
   if (!fail_sent) {
     spdlog::trace("Couldn't send failure message!");
     return State::Close;

src/coordinator/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(coordinator_src_files
+    coordinator.cpp
+    shard_map.cpp)
+
+find_package(fmt REQUIRED)
+find_package(Threads REQUIRED)
+
+add_library(mg-coordinator STATIC ${coordinator_src_files})
+target_link_libraries(mg-coordinator stdc++fs Threads::Threads fmt::fmt mg-utils mg-storage-v3)

src/coordinator/coordinator.cpp

@@ -0,0 +1,129 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include <coordinator/coordinator.hpp>
+
+namespace memgraph::coordinator {
+
+CoordinatorWriteResponses Coordinator::ApplyWrite(HeartbeatRequest &&heartbeat_request) {
+  spdlog::info("Coordinator handling HeartbeatRequest");
+
+  // add this storage engine to any under-replicated shards that it is not already a part of
+
+  auto initializing_rsms_for_shard_manager =
+      shard_map_.AssignShards(heartbeat_request.from_storage_manager, heartbeat_request.initialized_rsms);
+
+  return HeartbeatResponse{
+      .shards_to_initialize = initializing_rsms_for_shard_manager,
+  };
+}
+
+CoordinatorWriteResponses Coordinator::ApplyWrite(HlcRequest &&hlc_request) {
+  HlcResponse res{};
+
+  auto hlc_shard_map = shard_map_.GetHlc();
+
+  MG_ASSERT(!(hlc_request.last_shard_map_version.logical_id > hlc_shard_map.logical_id));
+
+  res.new_hlc = Hlc{
+      .logical_id = ++highest_allocated_timestamp_,
+      // TODO(tyler) probably pass some more context to the Coordinator here
+      // so that we can use our wall clock and enforce monotonicity.
+      // .coordinator_wall_clock = io_.Now(),
+  };
+
+  // Allways return fresher shard_map for now.
+  res.fresher_shard_map = std::make_optional(shard_map_);
+
+  return res;
+}
+
+CoordinatorWriteResponses Coordinator::ApplyWrite(AllocateEdgeIdBatchRequest &&ahr) {
+  AllocateEdgeIdBatchResponse res{};
+
+  uint64_t low = highest_allocated_edge_id_;
+
+  highest_allocated_edge_id_ += ahr.batch_size;
+
+  uint64_t high = highest_allocated_edge_id_;
+
+  res.low = low;
+  res.high = high;
+
+  return res;
+}
+
+/// This splits the shard immediately beneath the provided
+/// split key, keeping the assigned peers identical for now,
+/// but letting them be gradually migrated over time.
+CoordinatorWriteResponses Coordinator::ApplyWrite(SplitShardRequest &&split_shard_request) {
+  SplitShardResponse res{};
+
+  if (split_shard_request.previous_shard_map_version != shard_map_.shard_map_version) {
+    res.success = false;
+  } else {
+    res.success = shard_map_.SplitShard(split_shard_request.previous_shard_map_version, split_shard_request.label_id,
+                                        split_shard_request.split_key);
+  }
+
+  return res;
+}
+
+/// This adds the provided storage engine to the standby storage engine pool,
+/// which can be used to rebalance storage over time.
+CoordinatorWriteResponses Coordinator::ApplyWrite(
+    RegisterStorageEngineRequest && /* register_storage_engine_request */) {
+  RegisterStorageEngineResponse res{};
+  // TODO
+
+  return res;
+}
+
+/// This begins the process of draining the provided storage engine from all raft
+/// clusters that it might be participating in.
+CoordinatorWriteResponses Coordinator::ApplyWrite(
+    DeregisterStorageEngineRequest && /* register_storage_engine_request */) {
+  DeregisterStorageEngineResponse res{};
+  // TODO
+
+  return res;
+}
+
+CoordinatorWriteResponses Coordinator::ApplyWrite(InitializeLabelRequest &&initialize_label_request) {
+  InitializeLabelResponse res{};
+
+  std::optional<LabelId> new_label_id = shard_map_.InitializeNewLabel(
+      initialize_label_request.label_name, initialize_label_request.schema, initialize_label_request.replication_factor,
+      initialize_label_request.last_shard_map_version);
+
+  if (new_label_id) {
+    res.new_label_id = new_label_id.value();
+    res.fresher_shard_map = std::nullopt;
+    res.success = true;
+  } else {
+    res.fresher_shard_map = shard_map_;
+    res.success = false;
+  }
+
+  return res;
+}
+
+CoordinatorWriteResponses Coordinator::ApplyWrite(AllocatePropertyIdsRequest &&allocate_property_ids_request) {
+  AllocatePropertyIdsResponse res{};
+
+  auto property_ids = shard_map_.AllocatePropertyIds(allocate_property_ids_request.property_names);
+
+  res.property_ids = property_ids;
+
+  return res;
+}
+
+}  // namespace memgraph::coordinator

src/coordinator/coordinator.hpp

@@ -0,0 +1,196 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <optional>
+#include <set>
+#include <string>
+#include <unordered_set>
+#include <variant>
+#include <vector>
+
+#include <boost/uuid/uuid.hpp>
+
+#include <coordinator/hybrid_logical_clock.hpp>
+#include <coordinator/shard_map.hpp>
+#include <io/simulator/simulator.hpp>
+#include <io/time.hpp>
+#include <io/transport.hpp>
+#include <storage/v3/id_types.hpp>
+#include <storage/v3/schemas.hpp>
+
+namespace memgraph::coordinator {
+
+using memgraph::io::Address;
+using memgraph::storage::v3::LabelId;
+using memgraph::storage::v3::PropertyId;
+using memgraph::storage::v3::SchemaProperty;
+using SimT = memgraph::io::simulator::SimulatorTransport;
+using PrimaryKey = std::vector<PropertyValue>;
+
+struct HlcRequest {
+  Hlc last_shard_map_version;
+};
+
+struct HlcResponse {
+  Hlc new_hlc;
+  std::optional<ShardMap> fresher_shard_map;
+};
+
+struct GetShardMapRequest {
+  // No state
+};
+
+struct GetShardMapResponse {
+  ShardMap shard_map;
+};
+
+struct AllocateHlcBatchRequest {
+  Hlc low;
+  Hlc high;
+};
+
+struct AllocateHlcBatchResponse {
+  bool success;
+  Hlc low;
+  Hlc high;
+};
+
+struct AllocateEdgeIdBatchRequest {
+  size_t batch_size;
+};
+
+struct AllocateEdgeIdBatchResponse {
+  uint64_t low;
+  uint64_t high;
+};
+
+struct AllocatePropertyIdsRequest {
+  std::vector<std::string> property_names;
+};
+
+struct AllocatePropertyIdsResponse {
+  std::map<std::string, PropertyId> property_ids;
+};
+
+struct SplitShardRequest {
+  Hlc previous_shard_map_version;
+  LabelId label_id;
+  PrimaryKey split_key;
+};
+
+struct SplitShardResponse {
+  bool success;
+};
+
+struct RegisterStorageEngineRequest {
+  Address address;
+};
+
+struct RegisterStorageEngineResponse {
+  bool success;
+};
+
+struct DeregisterStorageEngineRequest {
+  Address address;
+};
+
+struct DeregisterStorageEngineResponse {
+  bool success;
+};
+
+struct InitializeLabelRequest {
+  std::string label_name;
+  std::vector<SchemaProperty> schema;
+  size_t replication_factor;
+  Hlc last_shard_map_version;
+};
+
+struct InitializeLabelResponse {
+  bool success;
+  LabelId new_label_id;
+  std::optional<ShardMap> fresher_shard_map;
+};
+
+struct HeartbeatRequest {
+  Address from_storage_manager;
+  std::set<boost::uuids::uuid> initialized_rsms;
+};
+
+struct HeartbeatResponse {
+  std::vector<ShardToInitialize> shards_to_initialize;
+};
+
+using CoordinatorWriteRequests =
+    std::variant<HlcRequest, AllocateEdgeIdBatchRequest, SplitShardRequest, RegisterStorageEngineRequest,
+                 DeregisterStorageEngineRequest, InitializeLabelRequest, AllocatePropertyIdsRequest, HeartbeatRequest>;
+using CoordinatorWriteResponses = std::variant<HlcResponse, AllocateEdgeIdBatchResponse, SplitShardResponse,
+                                               RegisterStorageEngineResponse, DeregisterStorageEngineResponse,
+                                               InitializeLabelResponse, AllocatePropertyIdsResponse, HeartbeatResponse>;
+
+using CoordinatorReadRequests = std::variant<GetShardMapRequest>;
+using CoordinatorReadResponses = std::variant<GetShardMapResponse>;
+
+class Coordinator {
+ public:
+  explicit Coordinator(ShardMap sm) : shard_map_{std::move(sm)} {}
+
+  // NOLINTNEXTLINE(readability-convert-member-functions-to-static
+  CoordinatorReadResponses Read(CoordinatorReadRequests requests) {
+    return std::visit([&](auto &&request) { return HandleRead(std::forward<decltype(request)>(request)); },
+                      std::move(requests));  // NOLINT(hicpp-move-const-arg,performance-move-const-arg)
+  }
+
+  // NOLINTNEXTLINE(readability-convert-member-functions-to-static
+  CoordinatorWriteResponses Apply(CoordinatorWriteRequests requests) {
+    return std::visit([&](auto &&request) mutable { return ApplyWrite(std::forward<decltype(request)>(request)); },
+                      std::move(requests));
+  }
+
+ private:
+  ShardMap shard_map_;
+  uint64_t highest_allocated_timestamp_;
+
+  /// Query engines need to periodically request batches of unique edge IDs.
+  uint64_t highest_allocated_edge_id_;
+
+  CoordinatorReadResponses HandleRead(GetShardMapRequest && /* get_shard_map_request */) {
+    GetShardMapResponse res;
+    res.shard_map = shard_map_;
+    return res;
+  }
+
+  CoordinatorWriteResponses ApplyWrite(HeartbeatRequest &&heartbeat_request);
+
+  CoordinatorWriteResponses ApplyWrite(HlcRequest &&hlc_request);
+
+  CoordinatorWriteResponses ApplyWrite(AllocateEdgeIdBatchRequest &&ahr);
+
+  /// This splits the shard immediately beneath the provided
+  /// split key, keeping the assigned peers identical for now,
+  /// but letting them be gradually migrated over time.
+  CoordinatorWriteResponses ApplyWrite(SplitShardRequest &&split_shard_request);
+
+  /// This adds the provided storage engine to the standby storage engine pool,
+  /// which can be used to rebalance storage over time.
+  static CoordinatorWriteResponses ApplyWrite(RegisterStorageEngineRequest && /* register_storage_engine_request */);
+
+  /// This begins the process of draining the provided storage engine from all raft
+  /// clusters that it might be participating in.
+  static CoordinatorWriteResponses ApplyWrite(DeregisterStorageEngineRequest && /* register_storage_engine_request */);
+
+  CoordinatorWriteResponses ApplyWrite(InitializeLabelRequest &&initialize_label_request);
+
+  CoordinatorWriteResponses ApplyWrite(AllocatePropertyIdsRequest &&allocate_property_ids_request);
+};
+
+}  // namespace memgraph::coordinator

src/coordinator/coordinator_client.hpp

@@ -0,0 +1,24 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "coordinator/coordinator.hpp"
+#include "io/rsm/rsm_client.hpp"
+
+namespace memgraph::coordinator {
+
+using memgraph::io::rsm::RsmClient;
+
+template <typename IoImpl>
+using CoordinatorClient = RsmClient<IoImpl, CoordinatorWriteRequests, CoordinatorWriteResponses,
+                                    CoordinatorReadRequests, CoordinatorReadResponses>;
+}  // namespace memgraph::coordinator

src/coordinator/coordinator_rsm.hpp

@@ -0,0 +1,23 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "coordinator/coordinator.hpp"
+#include "io/rsm/raft.hpp"
+
+namespace memgraph::coordinator {
+
+template <typename IoImpl>
+using CoordinatorRsm = memgraph::io::rsm::Raft<IoImpl, Coordinator, CoordinatorWriteRequests, CoordinatorWriteResponses,
+                                               CoordinatorReadRequests, CoordinatorReadResponses>;
+
+}  // namespace memgraph::coordinator

src/coordinator/hybrid_logical_clock.hpp

@@ -0,0 +1,36 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <compare>
+
+#include "io/time.hpp"
+
+namespace memgraph::coordinator {
+
+using Time = memgraph::io::Time;
+
+/// Hybrid-logical clock
+struct Hlc {
+  uint64_t logical_id;
+  Time coordinator_wall_clock;
+
+  auto operator<=>(const Hlc &other) const { return logical_id <=> other.logical_id; }
+
+  bool operator==(const Hlc &other) const = default;
+  bool operator<(const Hlc &other) const = default;
+  bool operator==(const uint64_t other) const { return logical_id == other; }
+  bool operator<(const uint64_t other) const { return logical_id < other; }
+  bool operator>=(const uint64_t other) const { return logical_id >= other; }
+};
+
+}  // namespace memgraph::coordinator

src/coordinator/shard_map.cpp

@@ -0,0 +1,90 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "coordinator/shard_map.hpp"
+#include "storage/v3/temporal.hpp"
+
+namespace memgraph::coordinator {
+
+using memgraph::common::SchemaType;
+using memgraph::storage::v3::TemporalData;
+using memgraph::storage::v3::TemporalType;
+
+PrimaryKey SchemaToMinKey(const std::vector<SchemaProperty> &schema) {
+  PrimaryKey ret{};
+
+  const int64_t min_int = std::numeric_limits<int64_t>::min();
+
+  const TemporalData date{TemporalType::Date, min_int};
+  const TemporalData local_time{TemporalType::LocalTime, min_int};
+  const TemporalData local_date_time{TemporalType::LocalDateTime, min_int};
+  const TemporalData duration{TemporalType::Duration, min_int};
+
+  for (const auto &schema_property : schema) {
+    switch (schema_property.type) {
+      case SchemaType::BOOL:
+        ret.emplace_back(PropertyValue(false));
+        break;
+      case SchemaType::INT:
+        ret.emplace_back(PropertyValue(min_int));
+        break;
+      case SchemaType::STRING:
+        ret.emplace_back(PropertyValue(""));
+        break;
+      case SchemaType::DATE:
+        ret.emplace_back(PropertyValue(date));
+        break;
+      case SchemaType::LOCALTIME:
+        ret.emplace_back(PropertyValue(local_time));
+        break;
+      case SchemaType::LOCALDATETIME:
+        ret.emplace_back(PropertyValue(local_date_time));
+        break;
+      case SchemaType::DURATION:
+        ret.emplace_back(PropertyValue(duration));
+        break;
+    }
+  }
+
+  return ret;
+}
+
+std::optional<LabelId> ShardMap::InitializeNewLabel(std::string label_name, std::vector<SchemaProperty> schema,
+                                                    size_t replication_factor, Hlc last_shard_map_version) {
+  if (shard_map_version != last_shard_map_version || labels.contains(label_name)) {
+    return std::nullopt;
+  }
+
+  const LabelId label_id = LabelId::FromUint(++max_label_id);
+
+  labels.emplace(std::move(label_name), label_id);
+
+  PrimaryKey initial_key = SchemaToMinKey(schema);
+  Shard empty_shard = {};
+
+  Shards shards = {
+      {initial_key, empty_shard},
+  };
+
+  LabelSpace label_space{
+      .schema = std::move(schema),
+      .shards = shards,
+      .replication_factor = replication_factor,
+  };
+
+  label_spaces.emplace(label_id, label_space);
+
+  IncrementShardMapVersion();
+
+  return label_id;
+}
+
+}  // namespace memgraph::coordinator

src/coordinator/shard_map.hpp

@@ -0,0 +1,276 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <limits>
+#include <map>
+#include <set>
+#include <vector>
+
+#include <boost/uuid/uuid.hpp>
+#include <boost/uuid/uuid_generators.hpp>
+
+#include "common/types.hpp"
+#include "coordinator/hybrid_logical_clock.hpp"
+#include "io/address.hpp"
+#include "storage/v3/config.hpp"
+#include "storage/v3/id_types.hpp"
+#include "storage/v3/property_value.hpp"
+#include "storage/v3/schemas.hpp"
+#include "storage/v3/temporal.hpp"
+
+namespace memgraph::coordinator {
+
+using memgraph::io::Address;
+using memgraph::storage::v3::Config;
+using memgraph::storage::v3::LabelId;
+using memgraph::storage::v3::PropertyId;
+using memgraph::storage::v3::PropertyValue;
+using memgraph::storage::v3::SchemaProperty;
+
+enum class Status : uint8_t {
+  CONSENSUS_PARTICIPANT,
+  INITIALIZING,
+  // TODO(tyler) this will possibly have more states,
+  // depending on the reconfiguration protocol that we
+  // implement.
+};
+
+struct AddressAndStatus {
+  memgraph::io::Address address;
+  Status status;
+  friend bool operator<(const AddressAndStatus &lhs, const AddressAndStatus &rhs) { return lhs.address < rhs.address; }
+};
+
+using PrimaryKey = std::vector<PropertyValue>;
+using Shard = std::vector<AddressAndStatus>;
+using Shards = std::map<PrimaryKey, Shard>;
+using LabelName = std::string;
+using PropertyName = std::string;
+using PropertyMap = std::map<PropertyName, PropertyId>;
+
+struct ShardToInitialize {
+  boost::uuids::uuid uuid;
+  LabelId label_id;
+  PrimaryKey min_key;
+  std::optional<PrimaryKey> max_key;
+  Config config;
+};
+
+PrimaryKey SchemaToMinKey(const std::vector<SchemaProperty> &schema);
+
+struct LabelSpace {
+  std::vector<SchemaProperty> schema;
+  std::map<PrimaryKey, Shard> shards;
+  size_t replication_factor;
+};
+
+struct ShardMap {
+  Hlc shard_map_version;
+  uint64_t max_property_id;
+  std::map<PropertyName, PropertyId> properties;
+  uint64_t max_label_id;
+  std::map<LabelName, LabelId> labels;
+  std::map<LabelId, LabelSpace> label_spaces;
+  std::map<LabelId, std::vector<SchemaProperty>> schemas;
+
+  Shards GetShards(const LabelName &label) {
+    const auto id = labels.at(label);
+    auto &shards = label_spaces.at(id).shards;
+    return shards;
+  }
+
+  // TODO(gabor) later we will want to update the wallclock time with
+  // the given Io<impl>'s time as well
+  Hlc IncrementShardMapVersion() noexcept {
+    ++shard_map_version.logical_id;
+    return shard_map_version;
+  }
+
+  Hlc GetHlc() const noexcept { return shard_map_version; }
+
+  // Returns the shard UUIDs that have been assigned but not yet acknowledged for this storage manager
+  std::vector<ShardToInitialize> AssignShards(Address storage_manager, std::set<boost::uuids::uuid> initialized) {
+    std::vector<ShardToInitialize> ret{};
+
+    bool mutated = false;
+
+    for (auto &[label_id, label_space] : label_spaces) {
+      for (auto &[low_key, shard] : label_space.shards) {
+        // TODO(tyler) avoid these triple-nested loops by having the heartbeat include better info
+        bool machine_contains_shard = false;
+
+        for (auto &aas : shard) {
+          if (initialized.contains(aas.address.unique_id)) {
+            spdlog::info("marking shard as full consensus participant: {}", aas.address.unique_id);
+            aas.status = Status::CONSENSUS_PARTICIPANT;
+            machine_contains_shard = true;
+          } else {
+            const bool same_machine = aas.address.last_known_ip == storage_manager.last_known_ip &&
+                                      aas.address.last_known_port == storage_manager.last_known_port;
+            if (same_machine) {
+              machine_contains_shard = true;
+              ret.push_back(ShardToInitialize{
+                  .uuid = aas.address.unique_id,
+                  .label_id = label_id,
+                  .min_key = low_key,
+                  .max_key = std::nullopt,
+                  .config = Config{},
+              });
+            }
+          }
+        }
+
+        if (!machine_contains_shard && shard.size() < label_space.replication_factor) {
+          Address address = storage_manager;
+
+          // TODO(tyler) use deterministic UUID so that coordinators don't diverge here
+          address.unique_id = boost::uuids::uuid{boost::uuids::random_generator()()},
+
+          ret.push_back(ShardToInitialize{
+              .uuid = address.unique_id,
+              .label_id = label_id,
+              .min_key = low_key,
+              .max_key = std::nullopt,
+              .config = Config{},
+          });
+
+          AddressAndStatus aas = {
+              .address = address,
+              .status = Status::INITIALIZING,
+          };
+
+          shard.emplace_back(aas);
+        }
+      }
+    }
+
+    if (mutated) {
+      IncrementShardMapVersion();
+    }
+
+    return ret;
+  }
+
+  bool SplitShard(Hlc previous_shard_map_version, LabelId label_id, const PrimaryKey &key) {
+    if (previous_shard_map_version != shard_map_version) {
+      return false;
+    }
+
+    auto &label_space = label_spaces.at(label_id);
+    auto &shards_in_map = label_space.shards;
+
+    MG_ASSERT(!shards_in_map.empty());
+    MG_ASSERT(!shards_in_map.contains(key));
+    MG_ASSERT(label_spaces.contains(label_id));
+
+    // Finding the Shard that the new PrimaryKey should map to.
+    auto prev = std::prev(shards_in_map.upper_bound(key));
+    Shard duplicated_shard = prev->second;
+
+    // Apply the split
+    shards_in_map[key] = duplicated_shard;
+
+    return true;
+  }
+
+  std::optional<LabelId> InitializeNewLabel(std::string label_name, std::vector<SchemaProperty> schema,
+                                            size_t replication_factor, Hlc last_shard_map_version);
+
+  void AddServer(Address server_address) {
+    // Find a random place for the server to plug in
+  }
+
+  LabelId GetLabelId(const std::string &label) const { return labels.at(label); }
+
+  Shards GetShardsForRange(const LabelName &label_name, const PrimaryKey &start_key, const PrimaryKey &end_key) const {
+    MG_ASSERT(start_key <= end_key);
+    MG_ASSERT(labels.contains(label_name));
+
+    LabelId label_id = labels.at(label_name);
+
+    const auto &label_space = label_spaces.at(label_id);
+
+    const auto &shards_for_label = label_space.shards;
+
+    MG_ASSERT(shards_for_label.begin()->first <= start_key,
+              "the ShardMap must always contain a minimal key that is less than or equal to any requested key");
+
+    auto it = std::prev(shards_for_label.upper_bound(start_key));
+    const auto end_it = shards_for_label.upper_bound(end_key);
+
+    Shards shards{};
+
+    std::copy(it, end_it, std::inserter(shards, shards.end()));
+
+    return shards;
+  }
+
+  Shard GetShardForKey(const LabelName &label_name, const PrimaryKey &key) const {
+    MG_ASSERT(labels.contains(label_name));
+
+    LabelId label_id = labels.at(label_name);
+
+    const auto &label_space = label_spaces.at(label_id);
+
+    MG_ASSERT(label_space.shards.begin()->first <= key,
+              "the ShardMap must always contain a minimal key that is less than or equal to any requested key");
+
+    return std::prev(label_space.shards.upper_bound(key))->second;
+  }
+
+  Shard GetShardForKey(const LabelId &label_id, const PrimaryKey &key) const {
+    MG_ASSERT(label_spaces.contains(label_id));
+
+    const auto &label_space = label_spaces.at(label_id);
+
+    MG_ASSERT(label_space.shards.begin()->first <= key,
+              "the ShardMap must always contain a minimal key that is less than or equal to any requested key");
+
+    return std::prev(label_space.shards.upper_bound(key))->second;
+  }
+
+  PropertyMap AllocatePropertyIds(const std::vector<PropertyName> &new_properties) {
+    PropertyMap ret{};
+
+    bool mutated = false;
+
+    for (const auto &property_name : new_properties) {
+      if (properties.contains(property_name)) {
+        auto property_id = properties.at(property_name);
+        ret.emplace(property_name, property_id);
+      } else {
+        mutated = true;
+
+        const PropertyId property_id = PropertyId::FromUint(++max_property_id);
+        ret.emplace(property_name, property_id);
+        properties.emplace(property_name, property_id);
+      }
+    }
+
+    if (mutated) {
+      IncrementShardMapVersion();
+    }
+
+    return ret;
+  }
+
+  std::optional<PropertyId> GetPropertyId(const std::string &property_name) const {
+    if (properties.contains(property_name)) {
+      return properties.at(property_name);
+    }
+
+    return std::nullopt;
+  }
+};
+
+}  // namespace memgraph::coordinator

src/expr/CMakeLists.txt

@@ -0,0 +1,20 @@
+define_add_lcp(add_lcp_expr lcp_expr_cpp_files generated_lcp_expr_files)
+
+add_lcp_expr(semantic/symbol.lcp)
+
+add_custom_target(generate_lcp_expr DEPENDS ${generated_lcp_expr_files})
+
+set(mg_expr_sources
+    ${lcp_expr_cpp_files}
+    parsing.cpp)
+
+find_package(Boost REQUIRED)
+
+add_library(mg-expr STATIC ${mg_expr_sources})
+add_dependencies(mg-expr generate_lcp_expr)
+target_include_directories(mg-expr PUBLIC ${CMAKE_SOURCE_DIR}/include)
+target_include_directories(mg-expr PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+target_include_directories(mg-expr PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/ast)
+target_include_directories(mg-expr PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/interpret)
+target_include_directories(mg-expr PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/semantic)
+target_link_libraries(mg-expr cppitertools Boost::headers mg-utils mg-parser)

src/expr/ast.hpp

@@ -0,0 +1,35 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+#pragma once
+
+#ifndef MG_AST_INCLUDE_PATH
+#ifdef MG_CLANG_TIDY_CHECK
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define MG_AST_INCLUDE_PATH "query/v2/frontend/ast/ast.hpp"
+#else
+#error Missing AST include path
+#endif
+#endif
+
+#ifndef MG_INJECTED_NAMESPACE_NAME
+#ifdef MG_CLANG_TIDY_CHECK
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define MG_INJECTED_NAMESPACE_NAME memgraph::query::v2
+#else
+#error Missing AST namespace
+#endif
+#endif
+
+#include MG_AST_INCLUDE_PATH
+
+namespace memgraph::expr {
+using namespace MG_INJECTED_NAMESPACE_NAME;  // NOLINT(google-build-using-namespace)
+}  // namespace memgraph::expr

src/expr/ast/ast_visitor.hpp

@@ -0,0 +1,135 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "utils/visitor.hpp"
+
+namespace MG_INJECTED_NAMESPACE_NAME {
+
+// Forward declares for Tree visitors.
+class CypherQuery;
+class SingleQuery;
+class CypherUnion;
+class NamedExpression;
+class Identifier;
+class PropertyLookup;
+class LabelsTest;
+class Aggregation;
+class Function;
+class Reduce;
+class Coalesce;
+class Extract;
+class All;
+class Single;
+class Any;
+class None;
+class ParameterLookup;
+class CallProcedure;
+class Create;
+class Match;
+class Return;
+class With;
+class Pattern;
+class NodeAtom;
+class EdgeAtom;
+class PrimitiveLiteral;
+class ListLiteral;
+class MapLiteral;
+class OrOperator;
+class XorOperator;
+class AndOperator;
+class NotOperator;
+class AdditionOperator;
+class SubtractionOperator;
+class MultiplicationOperator;
+class DivisionOperator;
+class ModOperator;
+class UnaryPlusOperator;
+class UnaryMinusOperator;
+class IsNullOperator;
+class NotEqualOperator;
+class EqualOperator;
+class LessOperator;
+class GreaterOperator;
+class LessEqualOperator;
+class GreaterEqualOperator;
+class InListOperator;
+class SubscriptOperator;
+class ListSlicingOperator;
+class IfOperator;
+class Delete;
+class Where;
+class SetProperty;
+class SetProperties;
+class SetLabels;
+class RemoveProperty;
+class RemoveLabels;
+class Merge;
+class Unwind;
+class AuthQuery;
+class ExplainQuery;
+class ProfileQuery;
+class IndexQuery;
+class InfoQuery;
+class ConstraintQuery;
+class RegexMatch;
+class DumpQuery;
+class ReplicationQuery;
+class LockPathQuery;
+class LoadCsv;
+class FreeMemoryQuery;
+class TriggerQuery;
+class IsolationLevelQuery;
+class CreateSnapshotQuery;
+class StreamQuery;
+class SettingQuery;
+class VersionQuery;
+class Foreach;
+class SchemaQuery;
+
+using TreeCompositeVisitor = memgraph::utils::CompositeVisitor<
+    SingleQuery, CypherUnion, NamedExpression, OrOperator, XorOperator, AndOperator, NotOperator, AdditionOperator,
+    SubtractionOperator, MultiplicationOperator, DivisionOperator, ModOperator, NotEqualOperator, EqualOperator,
+    LessOperator, GreaterOperator, LessEqualOperator, GreaterEqualOperator, InListOperator, SubscriptOperator,
+    ListSlicingOperator, IfOperator, UnaryPlusOperator, UnaryMinusOperator, IsNullOperator, ListLiteral, MapLiteral,
+    PropertyLookup, LabelsTest, Aggregation, Function, Reduce, Coalesce, Extract, All, Single, Any, None, CallProcedure,
+    Create, Match, Return, With, Pattern, NodeAtom, EdgeAtom, Delete, Where, SetProperty, SetProperties, SetLabels,
+    RemoveProperty, RemoveLabels, Merge, Unwind, RegexMatch, LoadCsv, Foreach>;
+
+using TreeLeafVisitor = memgraph::utils::LeafVisitor<Identifier, PrimitiveLiteral, ParameterLookup>;
+
+class HierarchicalTreeVisitor : public TreeCompositeVisitor, public TreeLeafVisitor {
+ public:
+  using TreeCompositeVisitor::PostVisit;
+  using TreeCompositeVisitor::PreVisit;
+  using TreeLeafVisitor::Visit;
+  using typename TreeLeafVisitor::ReturnType;
+};
+
+template <class TResult>
+class ExpressionVisitor
+    : public memgraph::utils::Visitor<
+          TResult, NamedExpression, OrOperator, XorOperator, AndOperator, NotOperator, AdditionOperator,
+          SubtractionOperator, MultiplicationOperator, DivisionOperator, ModOperator, NotEqualOperator, EqualOperator,
+          LessOperator, GreaterOperator, LessEqualOperator, GreaterEqualOperator, InListOperator, SubscriptOperator,
+          ListSlicingOperator, IfOperator, UnaryPlusOperator, UnaryMinusOperator, IsNullOperator, ListLiteral,
+          MapLiteral, PropertyLookup, LabelsTest, Aggregation, Function, Reduce, Coalesce, Extract, All, Single, Any,
+          None, ParameterLookup, Identifier, PrimitiveLiteral, RegexMatch> {};
+
+template <class TResult>
+class QueryVisitor
+    : public memgraph::utils::Visitor<TResult, CypherQuery, ExplainQuery, ProfileQuery, IndexQuery, AuthQuery,
+                                      InfoQuery, ConstraintQuery, DumpQuery, ReplicationQuery, LockPathQuery,
+                                      FreeMemoryQuery, TriggerQuery, IsolationLevelQuery, CreateSnapshotQuery,
+                                      StreamQuery, SettingQuery, VersionQuery, SchemaQuery> {};
+
+}  // namespace MG_INJECTED_NAMESPACE_NAME

src/expr/ast/pretty_print.hpp

@@ -0,0 +1,271 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <iostream>
+#include <type_traits>
+
+#include "expr/ast.hpp"
+#include "expr/typed_value.hpp"
+#include "utils/algorithm.hpp"
+#include "utils/logging.hpp"
+#include "utils/string.hpp"
+
+namespace memgraph::expr {
+namespace detail {
+template <typename T>
+void PrintObject(std::ostream *out, const T &arg) {
+  static_assert(!std::is_convertible<T, Expression *>::value,
+                "This overload shouldn't be called with pointers convertible "
+                "to Expression *. This means your other PrintObject overloads aren't "
+                "being called for certain AST nodes when they should (or perhaps such "
+                "overloads don't exist yet).");
+  *out << arg;
+}
+
+inline void PrintObject(std::ostream *out, const std::string &str) { *out << utils::Escape(str); }
+
+inline void PrintObject(std::ostream *out, Aggregation::Op op) { *out << Aggregation::OpToString(op); }
+
+inline void PrintObject(std::ostream *out, Expression *expr);
+
+inline void PrintObject(std::ostream *out, Identifier *expr) { PrintObject(out, static_cast<Expression *>(expr)); }
+
+template <typename T>
+void PrintObject(std::ostream *out, const std::vector<T> &vec) {
+  *out << "[";
+  utils::PrintIterable(*out, vec, ", ", [](auto &stream, const auto &item) { PrintObject(&stream, item); });
+  *out << "]";
+}
+
+template <typename T>
+void PrintObject(std::ostream *out, const std::vector<T, utils::Allocator<T>> &vec) {
+  *out << "[";
+  utils::PrintIterable(*out, vec, ", ", [](auto &stream, const auto &item) { PrintObject(&stream, item); });
+  *out << "]";
+}
+
+template <typename K, typename V>
+void PrintObject(std::ostream *out, const std::map<K, V> &map) {
+  *out << "{";
+  utils::PrintIterable(*out, map, ", ", [](auto &stream, const auto &item) {
+    PrintObject(&stream, item.first);
+    stream << ": ";
+    PrintObject(&stream, item.second);
+  });
+  *out << "}";
+}
+
+template <typename T>
+void PrintObject(std::ostream *out, const utils::pmr::map<utils::pmr::string, T> &map) {
+  *out << "{";
+  utils::PrintIterable(*out, map, ", ", [](auto &stream, const auto &item) {
+    PrintObject(&stream, item.first);
+    stream << ": ";
+    PrintObject(&stream, item.second);
+  });
+  *out << "}";
+}
+
+template <typename T1, typename T2, typename T3>
+inline void PrintObject(std::ostream *out, const TypedValueT<T1, T2, T3> &value) {
+  using TypedValue = TypedValueT<T1, T2, T3>;
+  switch (value.type()) {
+    case TypedValue::Type::Null:
+      *out << "null";
+      break;
+    case TypedValue::Type::String:
+      PrintObject(out, value.ValueString());
+      break;
+    case TypedValue::Type::Bool:
+      *out << (value.ValueBool() ? "true" : "false");
+      break;
+    case TypedValue::Type::Int:
+      PrintObject(out, value.ValueInt());
+      break;
+    case TypedValue::Type::Double:
+      PrintObject(out, value.ValueDouble());
+      break;
+    case TypedValue::Type::List:
+      PrintObject(out, value.ValueList());
+      break;
+    case TypedValue::Type::Map:
+      PrintObject(out, value.ValueMap());
+      break;
+    case TypedValue::Type::Date:
+      PrintObject(out, value.ValueDate());
+      break;
+    case TypedValue::Type::Duration:
+      PrintObject(out, value.ValueDuration());
+      break;
+    case TypedValue::Type::LocalTime:
+      PrintObject(out, value.ValueLocalTime());
+      break;
+    case TypedValue::Type::LocalDateTime:
+      PrintObject(out, value.ValueLocalDateTime());
+      break;
+    default:
+      MG_ASSERT(false, "PrintObject(std::ostream *out, const TypedValue &value) should not reach here");
+  }
+}
+
+template <typename T>
+void PrintOperatorArgs(std::ostream *out, const T &arg) {
+  *out << " ";
+  PrintObject(out, arg);
+  *out << ")";
+}
+
+template <typename T, typename... Ts>
+void PrintOperatorArgs(std::ostream *out, const T &arg, const Ts &...args) {
+  *out << " ";
+  PrintObject(out, arg);
+  PrintOperatorArgs(out, args...);
+}
+
+template <typename... Ts>
+void PrintOperator(std::ostream *out, const std::string &name, const Ts &...args) {
+  *out << "(" << name;
+  PrintOperatorArgs(out, args...);
+}
+}  // namespace detail
+
+class ExpressionPrettyPrinter : public ExpressionVisitor<void> {
+ public:
+  explicit ExpressionPrettyPrinter(std::ostream *out) : out_(out) {}
+
+  // Unary operators
+  // NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define UNARY_OPERATOR_VISIT(OP_NODE, OP_STR)      \
+  /* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
+  void Visit(OP_NODE &op) override { detail::PrintOperator(out_, OP_STR, op.expression_); }
+
+  UNARY_OPERATOR_VISIT(NotOperator, "Not");
+  UNARY_OPERATOR_VISIT(UnaryPlusOperator, "+");
+  UNARY_OPERATOR_VISIT(UnaryMinusOperator, "-");
+  UNARY_OPERATOR_VISIT(IsNullOperator, "IsNull");
+
+#undef UNARY_OPERATOR_VISIT
+
+  // Binary operators
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define BINARY_OPERATOR_VISIT(OP_NODE, OP_STR)     \
+  /* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
+  void Visit(OP_NODE &op) override { detail::PrintOperator(out_, OP_STR, op.expression1_, op.expression2_); }
+
+  BINARY_OPERATOR_VISIT(OrOperator, "Or");
+  BINARY_OPERATOR_VISIT(XorOperator, "Xor");
+  BINARY_OPERATOR_VISIT(AndOperator, "And");
+  BINARY_OPERATOR_VISIT(AdditionOperator, "+");
+  BINARY_OPERATOR_VISIT(SubtractionOperator, "-");
+  BINARY_OPERATOR_VISIT(MultiplicationOperator, "*");
+  BINARY_OPERATOR_VISIT(DivisionOperator, "/");
+  BINARY_OPERATOR_VISIT(ModOperator, "%");
+  BINARY_OPERATOR_VISIT(NotEqualOperator, "!=");
+  BINARY_OPERATOR_VISIT(EqualOperator, "==");
+  BINARY_OPERATOR_VISIT(LessOperator, "<");
+  BINARY_OPERATOR_VISIT(GreaterOperator, ">");
+  BINARY_OPERATOR_VISIT(LessEqualOperator, "<=");
+  BINARY_OPERATOR_VISIT(GreaterEqualOperator, ">=");
+  BINARY_OPERATOR_VISIT(InListOperator, "In");
+  BINARY_OPERATOR_VISIT(SubscriptOperator, "Subscript");
+
+#undef BINARY_OPERATOR_VISIT
+
+  // Other
+  void Visit(ListSlicingOperator &op) override {
+    detail::PrintOperator(out_, "ListSlicing", op.list_, op.lower_bound_, op.upper_bound_);
+  }
+
+  void Visit(IfOperator &op) override {
+    detail::PrintOperator(out_, "If", op.condition_, op.then_expression_, op.else_expression_);
+  }
+
+  void Visit(ListLiteral &op) override { detail::PrintOperator(out_, "ListLiteral", op.elements_); }
+
+  void Visit(MapLiteral &op) override {
+    std::map<std::string, Expression *> map;
+    for (const auto &kv : op.elements_) {
+      map[kv.first.name] = kv.second;
+    }
+    detail::PrintObject(out_, map);
+  }
+
+  void Visit(LabelsTest &op) override { detail::PrintOperator(out_, "LabelsTest", op.expression_); }
+
+  void Visit(Aggregation &op) override { detail::PrintOperator(out_, "Aggregation", op.op_); }
+
+  void Visit(Function &op) override { detail::PrintOperator(out_, "Function", op.function_name_, op.arguments_); }
+
+  void Visit(Reduce &op) override {
+    detail::PrintOperator(out_, "Reduce", op.accumulator_, op.initializer_, op.identifier_, op.list_, op.expression_);
+  }
+
+  void Visit(Coalesce &op) override { detail::PrintOperator(out_, "Coalesce", op.expressions_); }
+
+  void Visit(Extract &op) override { detail::PrintOperator(out_, "Extract", op.identifier_, op.list_, op.expression_); }
+
+  void Visit(All &op) override {
+    detail::PrintOperator(out_, "All", op.identifier_, op.list_expression_, op.where_->expression_);
+  }
+
+  void Visit(Single &op) override {
+    detail::PrintOperator(out_, "Single", op.identifier_, op.list_expression_, op.where_->expression_);
+  }
+
+  void Visit(Any &op) override {
+    detail::PrintOperator(out_, "Any", op.identifier_, op.list_expression_, op.where_->expression_);
+  }
+
+  void Visit(None &op) override {
+    detail::PrintOperator(out_, "None", op.identifier_, op.list_expression_, op.where_->expression_);
+  }
+
+  void Visit(Identifier &op) override { detail::PrintOperator(out_, "Identifier", op.name_); }
+
+  void Visit(PrimitiveLiteral &op) override { detail::PrintObject(out_, op.value_); }
+
+  void Visit(PropertyLookup &op) override {
+    detail::PrintOperator(out_, "PropertyLookup", op.expression_, op.property_.name);
+  }
+
+  void Visit(ParameterLookup &op) override { detail::PrintOperator(out_, "ParameterLookup", op.token_position_); }
+
+  void Visit(NamedExpression &op) override { detail::PrintOperator(out_, "NamedExpression", op.name_, op.expression_); }
+
+  void Visit(RegexMatch &op) override { detail::PrintOperator(out_, "=~", op.string_expr_, op.regex_); }
+
+ private:
+  std::ostream *out_;
+};
+
+namespace detail {
+inline void PrintObject(std::ostream *out, Expression *expr) {
+  if (expr) {
+    ExpressionPrettyPrinter printer{out};
+    expr->Accept(printer);
+  } else {
+    *out << "<null>";
+  }
+}
+}  // namespace detail
+
+inline void PrintExpression(Expression *expr, std::ostream *out) {
+  ExpressionPrettyPrinter printer{out};
+  expr->Accept(printer);
+}
+
+inline void PrintExpression(NamedExpression *expr, std::ostream *out) {
+  ExpressionPrettyPrinter printer{out};
+  expr->Accept(printer);
+}
+}  // namespace memgraph::expr

src/expr/exceptions.hpp

@@ -0,0 +1,52 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "utils/exceptions.hpp"
+
+namespace memgraph::expr {
+
+class SyntaxException : public utils::BasicException {
+ public:
+  using utils::BasicException::BasicException;
+  SyntaxException() : SyntaxException("") {}
+};
+
+class SemanticException : public utils::BasicException {
+ public:
+  using utils::BasicException::BasicException;
+  SemanticException() : BasicException("") {}
+};
+
+class ExpressionRuntimeException : public utils::BasicException {
+ public:
+  using utils::BasicException::BasicException;
+};
+
+class RedeclareVariableError : public SemanticException {
+ public:
+  explicit RedeclareVariableError(const std::string &name) : SemanticException("Redeclaring variable: " + name + ".") {}
+};
+
+class UnboundVariableError : public SemanticException {
+ public:
+  explicit UnboundVariableError(const std::string &name) : SemanticException("Unbound variable: " + name + ".") {}
+};
+
+class TypeMismatchError : public SemanticException {
+ public:
+  TypeMismatchError(const std::string &name, const std::string &datum, const std::string &expected)
+      : SemanticException(fmt::format("Type mismatch: {} already defined as {}, expected {}.", name, datum, expected)) {
+  }
+};
+
+}  // namespace memgraph::expr

src/expr/interpret/eval.hpp

@@ -0,0 +1,826 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+/// @file
+#pragma once
+
+#include <algorithm>
+#include <limits>
+#include <map>
+#include <optional>
+#include <regex>
+#include <type_traits>
+#include <vector>
+
+#include "expr/ast.hpp"
+#include "expr/exceptions.hpp"
+#include "expr/interpret/frame.hpp"
+#include "expr/semantic/symbol_table.hpp"
+#include "utils/exceptions.hpp"
+
+namespace memgraph::expr {
+
+struct StorageTag {};
+struct QueryEngineTag {};
+
+template <typename TypedValue, typename EvaluationContext, typename DbAccessor, typename StorageView, typename LabelId,
+          typename PropertyValue, typename ConvFunctor, typename Error, typename Tag = StorageTag>
+class ExpressionEvaluator : public ExpressionVisitor<TypedValue> {
+ public:
+  ExpressionEvaluator(Frame<TypedValue> *frame, const SymbolTable &symbol_table, const EvaluationContext &ctx,
+                      DbAccessor *dba, StorageView view)
+      : frame_(frame), symbol_table_(&symbol_table), ctx_(&ctx), dba_(dba), view_(view) {}
+
+  using ExpressionVisitor<TypedValue>::Visit;
+
+  utils::MemoryResource *GetMemoryResource() const { return ctx_->memory; }
+
+  TypedValue Visit(NamedExpression &named_expression) override {
+    const auto &symbol = symbol_table_->at(named_expression);
+    auto value = named_expression.expression_->Accept(*this);
+    frame_->at(symbol) = value;
+    return value;
+  }
+
+  TypedValue Visit(Identifier &ident) override {
+    return TypedValue(frame_->at(symbol_table_->at(ident)), ctx_->memory);
+  }
+
+  // NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define BINARY_OPERATOR_VISITOR(OP_NODE, CPP_OP, CYPHER_OP)                                                         \
+  /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                                                  \
+  TypedValue Visit(OP_NODE &op) override {                                                                          \
+    auto val1 = op.expression1_->Accept(*this);                                                                     \
+    auto val2 = op.expression2_->Accept(*this);                                                                     \
+    try {                                                                                                           \
+      return val1 CPP_OP val2;                                                                                      \
+    } catch (const TypedValueException &) {                                                                         \
+      throw ExpressionRuntimeException("Invalid types: {} and {} for '{}'.", val1.type(), val2.type(), #CYPHER_OP); \
+    }                                                                                                               \
+  }
+
+  // NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define UNARY_OPERATOR_VISITOR(OP_NODE, CPP_OP, CYPHER_OP)                                   \
+  /* NOLINTNEXTLINE(bugprone-macro-parentheses) */                                           \
+  TypedValue Visit(OP_NODE &op) override {                                                   \
+    auto val = op.expression_->Accept(*this);                                                \
+    try {                                                                                    \
+      return CPP_OP val;                                                                     \
+    } catch (const TypedValueException &) {                                                  \
+      throw ExpressionRuntimeException("Invalid type {} for '{}'.", val.type(), #CYPHER_OP); \
+    }                                                                                        \
+  }
+
+  BINARY_OPERATOR_VISITOR(OrOperator, ||, OR);
+  BINARY_OPERATOR_VISITOR(XorOperator, ^, XOR);
+  BINARY_OPERATOR_VISITOR(AdditionOperator, +, +);
+  BINARY_OPERATOR_VISITOR(SubtractionOperator, -, -);
+  BINARY_OPERATOR_VISITOR(MultiplicationOperator, *, *);
+  BINARY_OPERATOR_VISITOR(DivisionOperator, /, /);
+  BINARY_OPERATOR_VISITOR(ModOperator, %, %);
+  BINARY_OPERATOR_VISITOR(NotEqualOperator, !=, <>);
+  BINARY_OPERATOR_VISITOR(EqualOperator, ==, =);
+  BINARY_OPERATOR_VISITOR(LessOperator, <, <);
+  BINARY_OPERATOR_VISITOR(GreaterOperator, >, >);
+  BINARY_OPERATOR_VISITOR(LessEqualOperator, <=, <=);
+  BINARY_OPERATOR_VISITOR(GreaterEqualOperator, >=, >=);
+
+  UNARY_OPERATOR_VISITOR(NotOperator, !, NOT);
+  UNARY_OPERATOR_VISITOR(UnaryPlusOperator, +, +);
+  UNARY_OPERATOR_VISITOR(UnaryMinusOperator, -, -);
+
+#undef BINARY_OPERATOR_VISITOR
+#undef UNARY_OPERATOR_VISITOR
+
+  TypedValue Visit(AndOperator &op) override {
+    auto value1 = op.expression1_->Accept(*this);
+    if (value1.IsBool() && !value1.ValueBool()) {
+      // If first expression is false, don't evaluate the second one.
+      return value1;
+    }
+    auto value2 = op.expression2_->Accept(*this);
+    try {
+      return value1 && value2;
+    } catch (const TypedValueException &) {
+      throw ExpressionRuntimeException("Invalid types: {} and {} for AND.", value1.type(), value2.type());
+    }
+  }
+
+  TypedValue Visit(IfOperator &if_operator) override {
+    auto condition = if_operator.condition_->Accept(*this);
+    if (condition.IsNull()) {
+      return if_operator.else_expression_->Accept(*this);
+    }
+    if (condition.type() != TypedValue::Type::Bool) {
+      // At the moment IfOperator is used only in CASE construct.
+      throw ExpressionRuntimeException("CASE expected boolean expression, got {}.", condition.type());
+    }
+    if (condition.ValueBool()) {
+      return if_operator.then_expression_->Accept(*this);
+    }
+    return if_operator.else_expression_->Accept(*this);
+  }
+
+  TypedValue Visit(InListOperator &in_list) override {
+    auto literal = in_list.expression1_->Accept(*this);
+    auto _list = in_list.expression2_->Accept(*this);
+    if (_list.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    // Exceptions have higher priority than returning nulls when list expression
+    // is not null.
+    if (_list.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("IN expected a list, got {}.", _list.type());
+    }
+    const auto &list = _list.ValueList();
+
+    // If literal is NULL there is no need to try to compare it with every
+    // element in the list since result of every comparison will be NULL. There
+    // is one special case that we must test explicitly: if list is empty then
+    // result is false since no comparison will be performed.
+    if (list.empty()) return TypedValue(false, ctx_->memory);
+    if (literal.IsNull()) return TypedValue(ctx_->memory);
+
+    auto has_null = false;
+    for (const auto &element : list) {
+      auto result = literal == element;
+      if (result.IsNull()) {
+        has_null = true;
+      } else if (result.ValueBool()) {
+        return TypedValue(true, ctx_->memory);
+      }
+    }
+    if (has_null) {
+      return TypedValue(ctx_->memory);
+    }
+    return TypedValue(false, ctx_->memory);
+  }
+
+  TypedValue Visit(SubscriptOperator &list_indexing) override {
+    auto lhs = list_indexing.expression1_->Accept(*this);
+    auto index = list_indexing.expression2_->Accept(*this);
+    if (!lhs.IsList() && !lhs.IsMap() && !lhs.IsVertex() && !lhs.IsEdge() && !lhs.IsNull())
+      throw ExpressionRuntimeException(
+          "Expected a list, a map, a node or an edge to index with '[]', got "
+          "{}.",
+          lhs.type());
+    if (lhs.IsNull() || index.IsNull()) return TypedValue(ctx_->memory);
+    if (lhs.IsList()) {
+      if (!index.IsInt())
+        throw ExpressionRuntimeException("Expected an integer as a list index, got {}.", index.type());
+      auto index_int = index.ValueInt();
+      // NOTE: Take non-const reference to list, so that we can move out the
+      // indexed element as the result.
+      auto &list = lhs.ValueList();
+      if (index_int < 0) {
+        index_int += static_cast<int64_t>(list.size());
+      }
+      if (index_int >= static_cast<int64_t>(list.size()) || index_int < 0) return TypedValue(ctx_->memory);
+      // NOTE: Explicit move is needed, so that we return the move constructed
+      // value and preserve the correct MemoryResource.
+      return std::move(list[index_int]);
+    }
+
+    if (lhs.IsMap()) {
+      if (!index.IsString())
+        throw ExpressionRuntimeException("Expected a string as a map index, got {}.", index.type());
+      // NOTE: Take non-const reference to map, so that we can move out the
+      // looked-up element as the result.
+      auto &map = lhs.ValueMap();
+      auto found = map.find(index.ValueString());
+      if (found == map.end()) return TypedValue(ctx_->memory);
+      // NOTE: Explicit move is needed, so that we return the move constructed
+      // value and preserve the correct MemoryResource.
+      return std::move(found->second);
+    }
+
+    if (lhs.IsVertex()) {
+      if (!index.IsString())
+        throw ExpressionRuntimeException("Expected a string as a property name, got {}.", index.type());
+      return TypedValue(GetProperty(lhs.ValueVertex(), index.ValueString()), ctx_->memory);
+    }
+
+    if (lhs.IsEdge()) {
+      if (!index.IsString())
+        throw ExpressionRuntimeException("Expected a string as a property name, got {}.", index.type());
+      return TypedValue(GetProperty(lhs.ValueEdge(), index.ValueString()), ctx_->memory);
+    }
+
+    // lhs is Null
+    return TypedValue(ctx_->memory);
+  }
+
+  TypedValue Visit(ListSlicingOperator &op) override {
+    // If some type is null we can't return null, because throwing exception
+    // on illegal type has higher priority.
+    auto is_null = false;
+    auto get_bound = [&](Expression *bound_expr, int64_t default_value) {
+      if (bound_expr) {
+        auto bound = bound_expr->Accept(*this);
+        if (bound.type() == TypedValue::Type::Null) {
+          is_null = true;
+        } else if (bound.type() != TypedValue::Type::Int) {
+          throw ExpressionRuntimeException("Expected an integer for a bound in list slicing, got {}.", bound.type());
+        }
+        return bound;
+      }
+      return TypedValue(default_value, ctx_->memory);
+    };
+    auto _upper_bound = get_bound(op.upper_bound_, std::numeric_limits<int64_t>::max());
+    auto _lower_bound = get_bound(op.lower_bound_, 0);
+
+    auto _list = op.list_->Accept(*this);
+    if (_list.type() == TypedValue::Type::Null) {
+      is_null = true;
+    } else if (_list.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("Expected a list to slice, got {}.", _list.type());
+    }
+
+    if (is_null) {
+      return TypedValue(ctx_->memory);
+    }
+    const auto &list = _list.ValueList();
+    auto normalise_bound = [&](int64_t bound) {
+      if (bound < 0) {
+        bound = static_cast<int64_t>(list.size()) + bound;
+      }
+      return std::max(static_cast<int64_t>(0), std::min(bound, static_cast<int64_t>(list.size())));
+    };
+    auto lower_bound = normalise_bound(_lower_bound.ValueInt());
+    auto upper_bound = normalise_bound(_upper_bound.ValueInt());
+    if (upper_bound <= lower_bound) {
+      return TypedValue(typename TypedValue::TVector(ctx_->memory), ctx_->memory);
+    }
+    return TypedValue(
+        typename TypedValue::TVector(list.begin() + lower_bound, list.begin() + upper_bound, ctx_->memory));
+  }
+
+  TypedValue Visit(IsNullOperator &is_null) override {
+    auto value = is_null.expression_->Accept(*this);
+    return TypedValue(value.IsNull(), ctx_->memory);
+  }
+
+  TypedValue Visit(PropertyLookup &property_lookup) override {
+    auto expression_result = property_lookup.expression_->Accept(*this);
+    auto maybe_date = [this](const auto &date, const auto &prop_name) -> std::optional<TypedValue> {
+      if (prop_name == "year") {
+        return TypedValue(date.year, ctx_->memory);
+      }
+      if (prop_name == "month") {
+        return TypedValue(date.month, ctx_->memory);
+      }
+      if (prop_name == "day") {
+        return TypedValue(date.day, ctx_->memory);
+      }
+      return std::nullopt;
+    };
+    auto maybe_local_time = [this](const auto &lt, const auto &prop_name) -> std::optional<TypedValue> {
+      if (prop_name == "hour") {
+        return TypedValue(lt.hour, ctx_->memory);
+      }
+      if (prop_name == "minute") {
+        return TypedValue(lt.minute, ctx_->memory);
+      }
+      if (prop_name == "second") {
+        return TypedValue(lt.second, ctx_->memory);
+      }
+      if (prop_name == "millisecond") {
+        return TypedValue(lt.millisecond, ctx_->memory);
+      }
+      if (prop_name == "microsecond") {
+        return TypedValue(lt.microsecond, ctx_->memory);
+      }
+      return std::nullopt;
+    };
+    auto maybe_duration = [this](const auto &dur, const auto &prop_name) -> std::optional<TypedValue> {
+      if (prop_name == "day") {
+        return TypedValue(dur.Days(), ctx_->memory);
+      }
+      if (prop_name == "hour") {
+        return TypedValue(dur.SubDaysAsHours(), ctx_->memory);
+      }
+      if (prop_name == "minute") {
+        return TypedValue(dur.SubDaysAsMinutes(), ctx_->memory);
+      }
+      if (prop_name == "second") {
+        return TypedValue(dur.SubDaysAsSeconds(), ctx_->memory);
+      }
+      if (prop_name == "millisecond") {
+        return TypedValue(dur.SubDaysAsMilliseconds(), ctx_->memory);
+      }
+      if (prop_name == "microsecond") {
+        return TypedValue(dur.SubDaysAsMicroseconds(), ctx_->memory);
+      }
+      if (prop_name == "nanosecond") {
+        return TypedValue(dur.SubDaysAsNanoseconds(), ctx_->memory);
+      }
+      return std::nullopt;
+    };
+    switch (expression_result.type()) {
+      case TypedValue::Type::Null:
+        return TypedValue(ctx_->memory);
+      case TypedValue::Type::Vertex:
+        return GetProperty(expression_result.ValueVertex(), property_lookup.property_);
+      case TypedValue::Type::Edge:
+        return GetProperty(expression_result.ValueEdge(), property_lookup.property_);
+      case TypedValue::Type::Map: {
+        // NOTE: Take non-const reference to map, so that we can move out the
+        // looked-up element as the result.
+        auto &map = expression_result.ValueMap();
+        auto found = map.find(property_lookup.property_.name.c_str());
+        if (found == map.end()) return TypedValue(ctx_->memory);
+        // NOTE: Explicit move is needed, so that we return the move constructed
+        // value and preserve the correct MemoryResource.
+        return std::move(found->second);
+      }
+      case TypedValue::Type::Duration: {
+        const auto &prop_name = property_lookup.property_.name;
+        const auto &dur = expression_result.ValueDuration();
+        if (auto dur_field = maybe_duration(dur, prop_name); dur_field) {
+          return std::move(*dur_field);
+        }
+        throw ExpressionRuntimeException("Invalid property name {} for Duration", prop_name);
+      }
+      case TypedValue::Type::Date: {
+        const auto &prop_name = property_lookup.property_.name;
+        const auto &date = expression_result.ValueDate();
+        if (auto date_field = maybe_date(date, prop_name); date_field) {
+          return std::move(*date_field);
+        }
+        throw ExpressionRuntimeException("Invalid property name {} for Date", prop_name);
+      }
+      case TypedValue::Type::LocalTime: {
+        const auto &prop_name = property_lookup.property_.name;
+        const auto &lt = expression_result.ValueLocalTime();
+        if (auto lt_field = maybe_local_time(lt, prop_name); lt_field) {
+          return std::move(*lt_field);
+        }
+        throw ExpressionRuntimeException("Invalid property name {} for LocalTime", prop_name);
+      }
+      case TypedValue::Type::LocalDateTime: {
+        const auto &prop_name = property_lookup.property_.name;
+        const auto &ldt = expression_result.ValueLocalDateTime();
+        if (auto date_field = maybe_date(ldt.date, prop_name); date_field) {
+          return std::move(*date_field);
+        }
+        if (auto lt_field = maybe_local_time(ldt.local_time, prop_name); lt_field) {
+          return std::move(*lt_field);
+        }
+        throw ExpressionRuntimeException("Invalid property name {} for LocalDateTime", prop_name);
+      }
+      default:
+        throw ExpressionRuntimeException("Only nodes, edges, maps and temporal types have properties to be looked-up.");
+    }
+  }
+
+  template <typename VertexAccessor, typename TTag = Tag,
+            typename TReturnType = std::enable_if_t<std::is_same_v<TTag, StorageTag>, bool>>
+  TReturnType HasLabelImpl(const VertexAccessor &vertex, const LabelIx &label, StorageTag /*tag*/) {
+    auto has_label = vertex.HasLabel(view_, GetLabel(label));
+    if (has_label.HasError() && has_label.GetError() == Error::NONEXISTENT_OBJECT) {
+      // This is a very nasty and temporary hack in order to make MERGE
+      // work. The old storage had the following logic when returning an
+      // `OLD` view: `return old ? old : new`. That means that if the
+      // `OLD` view didn't exist, it returned the NEW view. With this hack
+      // we simulate that behavior.
+      // TODO (mferencevic, teon.banek): Remove once MERGE is
+      // reimplemented.
+      has_label = vertex.HasLabel(StorageView::NEW, GetLabel(label));
+    }
+    if (has_label.HasError()) {
+      switch (has_label.GetError()) {
+        case Error::DELETED_OBJECT:
+          throw ExpressionRuntimeException("Trying to access labels on a deleted node.");
+        case Error::NONEXISTENT_OBJECT:
+          throw ExpressionRuntimeException("Trying to access labels from a node that doesn't exist.");
+        case Error::SERIALIZATION_ERROR:
+        case Error::VERTEX_HAS_EDGES:
+        case Error::PROPERTIES_DISABLED:
+          throw ExpressionRuntimeException("Unexpected error when accessing labels.");
+      }
+    }
+    return *has_label;
+  }
+
+  template <typename VertexAccessor, typename TTag = Tag,
+            typename TReturnType = std::enable_if_t<std::is_same_v<TTag, QueryEngineTag>, bool>>
+  TReturnType HasLabelImpl(const VertexAccessor &vertex, const LabelIx &label_ix, QueryEngineTag /*tag*/) {
+    auto label = typename VertexAccessor::Label{LabelId::FromUint(label_ix.ix)};
+    auto has_label = vertex.HasLabel(label);
+    return !has_label;
+  }
+
+  TypedValue Visit(LabelsTest &labels_test) override {
+    auto expression_result = labels_test.expression_->Accept(*this);
+    switch (expression_result.type()) {
+      case TypedValue::Type::Null:
+        return TypedValue(ctx_->memory);
+      case TypedValue::Type::Vertex: {
+        const auto &vertex = expression_result.ValueVertex();
+        if (std::ranges::all_of(labels_test.labels_, [&vertex, this](const auto label_test) {
+              return this->HasLabelImpl(vertex, label_test, Tag{});
+            })) {
+          return TypedValue(true, ctx_->memory);
+        }
+        return TypedValue(false, ctx_->memory);
+      }
+      default:
+        throw ExpressionRuntimeException("Only nodes have labels.");
+    }
+  }
+
+  TypedValue Visit(PrimitiveLiteral &literal) override {
+    // TODO: no need to evaluate constants, we can write it to frame in one
+    // of the previous phases.
+    return TypedValue(literal.value_, ctx_->memory);
+  }
+
+  TypedValue Visit(ListLiteral &literal) override {
+    typename TypedValue::TVector result(ctx_->memory);
+    result.reserve(literal.elements_.size());
+    for (const auto &expression : literal.elements_) result.emplace_back(expression->Accept(*this));
+    return TypedValue(result, ctx_->memory);
+  }
+
+  TypedValue Visit(MapLiteral &literal) override {
+    typename TypedValue::TMap result(ctx_->memory);
+    for (const auto &pair : literal.elements_) result.emplace(pair.first.name, pair.second->Accept(*this));
+    return TypedValue(result, ctx_->memory);
+  }
+
+  TypedValue Visit(Aggregation &aggregation) override {
+    return TypedValue(frame_->at(symbol_table_->at(aggregation)), ctx_->memory);
+  }
+
+  TypedValue Visit(Coalesce &coalesce) override {
+    auto &exprs = coalesce.expressions_;
+
+    if (exprs.size() == 0) {
+      throw ExpressionRuntimeException("'coalesce' requires at least one argument.");
+    }
+
+    for (int64_t i = 0; i < exprs.size(); ++i) {
+      TypedValue val(exprs[i]->Accept(*this), ctx_->memory);
+      if (!val.IsNull()) {
+        return val;
+      }
+    }
+
+    return TypedValue(ctx_->memory);
+  }
+
+  TypedValue Visit(Function &function) override {
+    FunctionContext function_ctx{dba_, ctx_->memory, ctx_->timestamp, &ctx_->counters, view_};
+    // Stack allocate evaluated arguments when there's a small number of them.
+    if (function.arguments_.size() <= 8) {
+      TypedValue arguments[8] = {TypedValue(ctx_->memory), TypedValue(ctx_->memory), TypedValue(ctx_->memory),
+                                 TypedValue(ctx_->memory), TypedValue(ctx_->memory), TypedValue(ctx_->memory),
+                                 TypedValue(ctx_->memory), TypedValue(ctx_->memory)};
+      for (size_t i = 0; i < function.arguments_.size(); ++i) {
+        arguments[i] = function.arguments_[i]->Accept(*this);
+      }
+      auto res = function.function_(arguments, function.arguments_.size(), function_ctx);
+      MG_ASSERT(res.GetMemoryResource() == ctx_->memory);
+      return res;
+    } else {
+      typename TypedValue::TVector arguments(ctx_->memory);
+      arguments.reserve(function.arguments_.size());
+      for (const auto &argument : function.arguments_) {
+        arguments.emplace_back(argument->Accept(*this));
+      }
+      auto res = function.function_(arguments.data(), arguments.size(), function_ctx);
+      MG_ASSERT(res.GetMemoryResource() == ctx_->memory);
+      return res;
+    }
+  }
+
+  TypedValue Visit(Reduce &reduce) override {
+    auto list_value = reduce.list_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("REDUCE expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &element_symbol = symbol_table_->at(*reduce.identifier_);
+    const auto &accumulator_symbol = symbol_table_->at(*reduce.accumulator_);
+    auto accumulator = reduce.initializer_->Accept(*this);
+    for (const auto &element : list) {
+      frame_->at(accumulator_symbol) = accumulator;
+      frame_->at(element_symbol) = element;
+      accumulator = reduce.expression_->Accept(*this);
+    }
+    return accumulator;
+  }
+
+  TypedValue Visit(Extract &extract) override {
+    auto list_value = extract.list_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("EXTRACT expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &element_symbol = symbol_table_->at(*extract.identifier_);
+    typename TypedValue::TVector result(ctx_->memory);
+    result.reserve(list.size());
+    for (const auto &element : list) {
+      if (element.IsNull()) {
+        result.emplace_back();
+      } else {
+        frame_->at(element_symbol) = element;
+        result.emplace_back(extract.expression_->Accept(*this));
+      }
+    }
+    return TypedValue(result, ctx_->memory);
+  }
+
+  TypedValue Visit(All &all) override {
+    auto list_value = all.list_expression_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("ALL expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &symbol = symbol_table_->at(*all.identifier_);
+    bool has_null_elements = false;
+    bool has_value = false;
+    for (const auto &element : list) {
+      frame_->at(symbol) = element;
+      auto result = all.where_->expression_->Accept(*this);
+      if (!result.IsNull() && result.type() != TypedValue::Type::Bool) {
+        throw ExpressionRuntimeException("Predicate of ALL must evaluate to boolean, got {}.", result.type());
+      }
+      if (!result.IsNull()) {
+        has_value = true;
+        if (!result.ValueBool()) {
+          return TypedValue(false, ctx_->memory);
+        }
+      } else {
+        has_null_elements = true;
+      }
+    }
+    if (!has_value) {
+      return TypedValue(ctx_->memory);
+    }
+    if (has_null_elements) {
+      return TypedValue(false, ctx_->memory);
+    } else {
+      return TypedValue(true, ctx_->memory);
+    }
+  }
+
+  TypedValue Visit(Single &single) override {
+    auto list_value = single.list_expression_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("SINGLE expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &symbol = symbol_table_->at(*single.identifier_);
+    bool has_value = false;
+    bool predicate_satisfied = false;
+    for (const auto &element : list) {
+      frame_->at(symbol) = element;
+      auto result = single.where_->expression_->Accept(*this);
+      if (!result.IsNull() && result.type() != TypedValue::Type::Bool) {
+        throw ExpressionRuntimeException("Predicate of SINGLE must evaluate to boolean, got {}.", result.type());
+      }
+      if (result.type() == TypedValue::Type::Bool) {
+        has_value = true;
+      }
+      if (result.IsNull() || !result.ValueBool()) {
+        continue;
+      }
+      // Return false if more than one element satisfies the predicate.
+      if (predicate_satisfied) {
+        return TypedValue(false, ctx_->memory);
+      } else {
+        predicate_satisfied = true;
+      }
+    }
+    if (!has_value) {
+      return TypedValue(ctx_->memory);
+    } else {
+      return TypedValue(predicate_satisfied, ctx_->memory);
+    }
+  }
+
+  TypedValue Visit(Any &any) override {
+    auto list_value = any.list_expression_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("ANY expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &symbol = symbol_table_->at(*any.identifier_);
+    bool has_value = false;
+    for (const auto &element : list) {
+      frame_->at(symbol) = element;
+      auto result = any.where_->expression_->Accept(*this);
+      if (!result.IsNull() && result.type() != TypedValue::Type::Bool) {
+        throw ExpressionRuntimeException("Predicate of ANY must evaluate to boolean, got {}.", result.type());
+      }
+      if (!result.IsNull()) {
+        has_value = true;
+        if (result.ValueBool()) {
+          return TypedValue(true, ctx_->memory);
+        }
+      }
+    }
+    // Return Null if all elements are Null
+    if (!has_value) {
+      return TypedValue(ctx_->memory);
+    } else {
+      return TypedValue(false, ctx_->memory);
+    }
+  }
+
+  TypedValue Visit(None &none) override {
+    auto list_value = none.list_expression_->Accept(*this);
+    if (list_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (list_value.type() != TypedValue::Type::List) {
+      throw ExpressionRuntimeException("NONE expected a list, got {}.", list_value.type());
+    }
+    const auto &list = list_value.ValueList();
+    const auto &symbol = symbol_table_->at(*none.identifier_);
+    bool has_value = false;
+    for (const auto &element : list) {
+      frame_->at(symbol) = element;
+      auto result = none.where_->expression_->Accept(*this);
+      if (!result.IsNull() && result.type() != TypedValue::Type::Bool) {
+        throw ExpressionRuntimeException("Predicate of NONE must evaluate to boolean, got {}.", result.type());
+      }
+      if (!result.IsNull()) {
+        has_value = true;
+        if (result.ValueBool()) {
+          return TypedValue(false, ctx_->memory);
+        }
+      }
+    }
+    // Return Null if all elements are Null
+    if (!has_value) {
+      return TypedValue(ctx_->memory);
+    } else {
+      return TypedValue(true, ctx_->memory);
+    }
+  }
+
+  TypedValue Visit(ParameterLookup &param_lookup) override {
+    return TypedValue(conv_(ctx_->parameters.AtTokenPosition(param_lookup.token_position_)), ctx_->memory);
+  }
+
+  TypedValue Visit(RegexMatch &regex_match) override {
+    auto target_string_value = regex_match.string_expr_->Accept(*this);
+    auto regex_value = regex_match.regex_->Accept(*this);
+    if (target_string_value.IsNull() || regex_value.IsNull()) {
+      return TypedValue(ctx_->memory);
+    }
+    if (regex_value.type() != TypedValue::Type::String) {
+      throw ExpressionRuntimeException("Regular expression must evaluate to a string, got {}.", regex_value.type());
+    }
+    if (target_string_value.type() != TypedValue::Type::String) {
+      // Instead of error, we return Null which makes it compatible in case we
+      // use indexed lookup which filters out any non-string properties.
+      // Assuming a property lookup is the target_string_value.
+      return TypedValue(ctx_->memory);
+    }
+    const auto &target_string = target_string_value.ValueString();
+    try {
+      std::regex regex(regex_value.ValueString());
+      return TypedValue(std::regex_match(target_string, regex), ctx_->memory);
+    } catch (const std::regex_error &e) {
+      throw ExpressionRuntimeException("Regex error in '{}': {}", regex_value.ValueString(), e.what());
+    }
+  }
+
+ private:
+  template <class TRecordAccessor, class TTag = Tag,
+            class TReturnType = std::enable_if_t<std::is_same_v<TTag, QueryEngineTag>, TypedValue>>
+  TReturnType GetProperty(const TRecordAccessor &record_accessor, PropertyIx prop) {
+    auto maybe_prop = record_accessor.GetProperty(prop.name);
+    // Handler non existent property
+    return conv_(maybe_prop);
+  }
+
+  template <class TRecordAccessor, class TTag = Tag,
+            class TReturnType = std::enable_if_t<std::is_same_v<TTag, QueryEngineTag>, TypedValue>>
+  TReturnType GetProperty(const TRecordAccessor &record_accessor, const std::string_view name) {
+    auto maybe_prop = record_accessor.GetProperty(std::string(name));
+    // Handler non existent property
+    return conv_(maybe_prop);
+  }
+
+  template <class TRecordAccessor, class TTag = Tag,
+            class TReturnType = std::enable_if_t<std::is_same_v<TTag, StorageTag>, TypedValue>>
+  TypedValue GetProperty(const TRecordAccessor &record_accessor, PropertyIx prop) {
+    auto maybe_prop = record_accessor.GetProperty(view_, ctx_->properties[prop.ix]);
+    if (maybe_prop.HasError() && maybe_prop.GetError() == Error::NONEXISTENT_OBJECT) {
+      // This is a very nasty and temporary hack in order to make MERGE work.
+      // The old storage had the following logic when returning an `OLD` view:
+      // `return old ? old : new`. That means that if the `OLD` view didn't
+      // exist, it returned the NEW view. With this hack we simulate that
+      // behavior.
+      // TODO (mferencevic, teon.banek): Remove once MERGE is reimplemented.
+      maybe_prop = record_accessor.GetProperty(StorageView::NEW, ctx_->properties[prop.ix]);
+    }
+    if (maybe_prop.HasError()) {
+      switch (maybe_prop.GetError()) {
+        case Error::DELETED_OBJECT:
+          throw ExpressionRuntimeException("Trying to get a property from a deleted object.");
+        case Error::NONEXISTENT_OBJECT:
+          throw ExpressionRuntimeException("Trying to get a property from an object that doesn't exist.");
+        case Error::SERIALIZATION_ERROR:
+        case Error::VERTEX_HAS_EDGES:
+        case Error::PROPERTIES_DISABLED:
+          throw ExpressionRuntimeException("Unexpected error when getting a property.");
+      }
+    }
+    return conv_(*maybe_prop, ctx_->memory);
+  }
+
+  template <class TRecordAccessor, class TTag = Tag,
+            class TReturnType = std::enable_if_t<std::is_same_v<TTag, StorageTag>, TypedValue>>
+  TypedValue GetProperty(const TRecordAccessor &record_accessor, const std::string_view name) {
+    auto maybe_prop = record_accessor.GetProperty(view_, dba_->NameToProperty(name));
+    if (maybe_prop.HasError() && maybe_prop.GetError() == Error::NONEXISTENT_OBJECT) {
+      // This is a very nasty and temporary hack in order to make MERGE work.
+      // The old storage had the following logic when returning an `OLD` view:
+      // `return old ? old : new`. That means that if the `OLD` view didn't
+      // exist, it returned the NEW view. With this hack we simulate that
+      // behavior.
+      // TODO (mferencevic, teon.banek): Remove once MERGE is reimplemented.
+      maybe_prop = record_accessor.GetProperty(view_, dba_->NameToProperty(name));
+    }
+    if (maybe_prop.HasError()) {
+      switch (maybe_prop.GetError()) {
+        case Error::DELETED_OBJECT:
+          throw ExpressionRuntimeException("Trying to get a property from a deleted object.");
+        case Error::NONEXISTENT_OBJECT:
+          throw ExpressionRuntimeException("Trying to get a property from an object that doesn't exist.");
+        case Error::SERIALIZATION_ERROR:
+        case Error::VERTEX_HAS_EDGES:
+        case Error::PROPERTIES_DISABLED:
+          throw ExpressionRuntimeException("Unexpected error when getting a property.");
+      }
+    }
+    return conv_(*maybe_prop, ctx_->memory);
+  }
+
+  LabelId GetLabel(LabelIx label) { return ctx_->labels[label.ix]; }
+
+  Frame<TypedValue> *frame_;
+  const SymbolTable *symbol_table_;
+  const EvaluationContext *ctx_;
+  DbAccessor *dba_;
+  // which switching approach should be used when evaluating
+  StorageView view_;
+  ConvFunctor conv_;
+};
+
+/// A helper function for evaluating an expression that's an int.
+///
+/// @param what - Name of what's getting evaluated. Used for user feedback (via
+///               exception) when the evaluated value is not an int.
+/// @throw ExpressionRuntimeException if expression doesn't evaluate to an int.
+template <typename ExpressionEvaluator>
+int64_t EvaluateInt(ExpressionEvaluator *evaluator, Expression *expr, const std::string &what) {
+  TypedValue value = expr->Accept(*evaluator);
+  try {
+    return value.ValueInt();
+  } catch (TypedValueException &e) {
+    throw ExpressionRuntimeException(what + " must be an int");
+  }
+}
+
+template <typename ExpressionEvaluator>
+std::optional<size_t> EvaluateMemoryLimit(ExpressionEvaluator *eval, Expression *memory_limit, size_t memory_scale) {
+  if (!memory_limit) return std::nullopt;
+  auto limit_value = memory_limit->Accept(*eval);
+  if (!limit_value.IsInt() || limit_value.ValueInt() <= 0)
+    throw ExpressionRuntimeException("Memory limit must be a non-negative integer.");
+  size_t limit = limit_value.ValueInt();
+  if (std::numeric_limits<size_t>::max() / memory_scale < limit)
+    throw ExpressionRuntimeException("Memory limit overflow.");
+  return limit * memory_scale;
+}
+
+}  // namespace memgraph::expr

src/expr/interpret/frame.hpp

@@ -0,0 +1,45 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <vector>
+
+#include "expr/semantic/symbol_table.hpp"
+#include "utils/logging.hpp"
+#include "utils/memory.hpp"
+#include "utils/pmr/vector.hpp"
+
+namespace memgraph::expr {
+
+template <typename TypedValue>
+class Frame {
+ public:
+  /// Create a Frame of given size backed by a utils::NewDeleteResource()
+  explicit Frame(int64_t size) : elems_(size, utils::NewDeleteResource()) { MG_ASSERT(size >= 0); }
+
+  Frame(int64_t size, utils::MemoryResource *memory) : elems_(size, memory) { MG_ASSERT(size >= 0); }
+
+  TypedValue &operator[](const Symbol &symbol) { return elems_[symbol.position()]; }
+  const TypedValue &operator[](const Symbol &symbol) const { return elems_[symbol.position()]; }
+
+  TypedValue &at(const Symbol &symbol) { return elems_.at(symbol.position()); }
+  const TypedValue &at(const Symbol &symbol) const { return elems_.at(symbol.position()); }
+
+  auto &elems() { return elems_; }
+
+  utils::MemoryResource *GetMemoryResource() const { return elems_.get_allocator().GetMemoryResource(); }
+
+ private:
+  utils::pmr::vector<TypedValue> elems_;
+};
+
+}  // namespace memgraph::expr

src/expr/parsing.cpp

@@ -0,0 +1,184 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "expr/parsing.hpp"
+
+#include <cctype>
+#include <codecvt>
+#include <locale>
+#include <stdexcept>
+
+#include "expr/exceptions.hpp"
+#include "utils/logging.hpp"
+#include "utils/string.hpp"
+
+namespace memgraph::expr {
+
+int64_t ParseIntegerLiteral(const std::string &s) {
+  try {
+    // Not really correct since long long can have a bigger range than int64_t.
+    return static_cast<int64_t>(std::stoll(s, 0, 0));
+  } catch (const std::out_of_range &) {
+    throw SemanticException("Integer literal exceeds 64 bits.");
+  }
+}
+
+std::string ParseStringLiteral(const std::string &s) {
+  // These functions is declared as lambda since its semantics is highly
+  // specific for this conxtext and shouldn't be used elsewhere.
+  auto EncodeEscapedUnicodeCodepointUtf32 = [](const std::string &s, int &i) {
+    const int kLongUnicodeLength = 8;
+    int j = i + 1;
+    while (j < static_cast<int>(s.size()) - 1 && j < i + kLongUnicodeLength + 1 && isxdigit(s[j])) {
+      ++j;
+    }
+    if (j - i == kLongUnicodeLength + 1) {
+      char32_t t = stoi(s.substr(i + 1, kLongUnicodeLength), 0, 16);
+      i += kLongUnicodeLength;
+      std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> converter;
+      return converter.to_bytes(t);
+    }
+    throw SyntaxException(
+        "Expected 8 hex digits as unicode codepoint started with \\U. "
+        "Use \\u for 4 hex digits format.");
+  };
+  auto EncodeEscapedUnicodeCodepointUtf16 = [](const std::string &s, int &i) {
+    const int kShortUnicodeLength = 4;
+    int j = i + 1;
+    while (j < static_cast<int>(s.size()) - 1 && j < i + kShortUnicodeLength + 1 && isxdigit(s[j])) {
+      ++j;
+    }
+    if (j - i >= kShortUnicodeLength + 1) {
+      char16_t t = stoi(s.substr(i + 1, kShortUnicodeLength), 0, 16);
+      if (t >= 0xD800 && t <= 0xDBFF) {
+        // t is high surrogate pair. Expect one more utf16 codepoint.
+        j = i + kShortUnicodeLength + 1;
+        if (j >= static_cast<int>(s.size()) - 1 || s[j] != '\\') {
+          throw SemanticException("Invalid UTF codepoint.");
+        }
+        ++j;
+        if (j >= static_cast<int>(s.size()) - 1 || (s[j] != 'u' && s[j] != 'U')) {
+          throw SemanticException("Invalid UTF codepoint.");
+        }
+        ++j;
+        int k = j;
+        while (k < static_cast<int>(s.size()) - 1 && k < j + kShortUnicodeLength && isxdigit(s[k])) {
+          ++k;
+        }
+        if (k != j + kShortUnicodeLength) {
+          throw SemanticException("Invalid UTF codepoint.");
+        }
+        char16_t surrogates[3] = {t, static_cast<char16_t>(stoi(s.substr(j, kShortUnicodeLength), 0, 16)), 0};
+        i += kShortUnicodeLength + 2 + kShortUnicodeLength;
+        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> converter;
+        return converter.to_bytes(surrogates);
+      } else {
+        i += kShortUnicodeLength;
+        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> converter;
+        return converter.to_bytes(t);
+      }
+    }
+    throw SyntaxException(
+        "Expected 4 hex digits as unicode codepoint started with \\u. "
+        "Use \\U for 8 hex digits format.");
+  };
+
+  std::string unescaped;
+  bool escape = false;
+
+  // First and last char is quote, we don't need to look at them.
+  for (int i = 1; i < static_cast<int>(s.size()) - 1; ++i) {
+    if (escape) {
+      switch (s[i]) {
+        case '\\':
+          unescaped += '\\';
+          break;
+        case '\'':
+          unescaped += '\'';
+          break;
+        case '"':
+          unescaped += '"';
+          break;
+        case 'B':
+        case 'b':
+          unescaped += '\b';
+          break;
+        case 'F':
+        case 'f':
+          unescaped += '\f';
+          break;
+        case 'N':
+        case 'n':
+          unescaped += '\n';
+          break;
+        case 'R':
+        case 'r':
+          unescaped += '\r';
+          break;
+        case 'T':
+        case 't':
+          unescaped += '\t';
+          break;
+        case 'U':
+          try {
+            unescaped += EncodeEscapedUnicodeCodepointUtf32(s, i);
+          } catch (const std::range_error &) {
+            throw SemanticException("Invalid UTF codepoint.");
+          }
+          break;
+        case 'u':
+          try {
+            unescaped += EncodeEscapedUnicodeCodepointUtf16(s, i);
+          } catch (const std::range_error &) {
+            throw SemanticException("Invalid UTF codepoint.");
+          }
+          break;
+        default:
+          // This should never happen, except grammar changes and we don't
+          // notice change in this production.
+          DLOG_FATAL("can't happen");
+          throw std::exception();
+      }
+      escape = false;
+    } else if (s[i] == '\\') {
+      escape = true;
+    } else {
+      unescaped += s[i];
+    }
+  }
+  return unescaped;
+}
+
+double ParseDoubleLiteral(const std::string &s) {
+  try {
+    return utils::ParseDouble(s);
+  } catch (const utils::BasicException &) {
+    throw SemanticException("Couldn't parse string to double.");
+  }
+}
+
+std::string ParseParameter(const std::string &s) {
+  DMG_ASSERT(s[0] == '$', "Invalid string passed as parameter name");
+  if (s[1] != '`') return s.substr(1);
+  // If parameter name is escaped symbolic name then symbolic name should be
+  // unescaped and leading and trailing backquote should be removed.
+  DMG_ASSERT(s.size() > 3U && s.back() == '`', "Invalid string passed as parameter name");
+  std::string out;
+  for (int i = 2; i < static_cast<int>(s.size()) - 1; ++i) {
+    if (s[i] == '`') {
+      ++i;
+    }
+    out.push_back(s[i]);
+  }
+  return out;
+}
+
+}  // namespace memgraph::expr

src/expr/parsing.hpp

@@ -0,0 +1,27 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+/// @file
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace memgraph::expr {
+
+// These are the functions for parsing literals and parameter names from
+// opencypher query.
+int64_t ParseIntegerLiteral(const std::string &s);
+std::string ParseStringLiteral(const std::string &s);
+double ParseDoubleLiteral(const std::string &s);
+std::string ParseParameter(const std::string &s);
+
+}  // namespace memgraph::expr

src/expr/semantic/symbol.lcp

@@ -0,0 +1,87 @@
+;; Copyright 2022 Memgraph Ltd.
+;;
+;; Use of this software is governed by the Business Source License
+;; included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+;; License, and you may not use this file except in compliance with the Business Source License.
+;;
+;; As of the Change Date specified in that file, in accordance with
+;; the Business Source License, use of this software will be governed
+;; by the Apache License, Version 2.0, included in the file
+;; licenses/APL.txt.
+
+#>cpp
+#pragma once
+
+#include <string>
+
+#include "utils/typeinfo.hpp"
+cpp<#
+
+(lcp:namespace memgraph)
+(lcp:namespace expr)
+
+(lcp:define-class symbol ()
+  ((name "std::string" :scope :public)
+   (position :int64_t :scope :public)
+   (user-declared :bool :initval "true" :scope :public)
+   (type "Type" :initval "Type::ANY" :scope :public)
+   (token-position :int64_t :initval "-1" :scope :public))
+  (:public
+    ;; This is similar to TypedValue::Type, but this has `Any` type.
+    ;; TODO: Make a better Type structure which can store a generic List.
+    (lcp:define-enum type (any vertex edge path number edge-list)
+      (:serialize))
+    #>cpp
+    // TODO: Generate enum to string conversion from LCP. Note, that this is
+    // displayed to the end user, so we may want to have a pretty name of each
+    // value.
+    static std::string TypeToString(Type type) {
+      const char *enum_string[] = {"Any",  "Vertex", "Edge",
+                                   "Path", "Number", "EdgeList"};
+      return enum_string[static_cast<int>(type)];
+    }
+
+    Symbol() {}
+    Symbol(const std::string &name, int position, bool user_declared,
+           Type type = Type::ANY, int token_position = -1)
+        : name_(name),
+          position_(position),
+          user_declared_(user_declared),
+          type_(type),
+          token_position_(token_position) {}
+
+    bool operator==(const Symbol &other) const {
+      return position_ == other.position_ && name_ == other.name_ &&
+             type_ == other.type_;
+    }
+    bool operator!=(const Symbol &other) const { return !operator==(other); }
+
+    // TODO: Remove these since members are public
+    const auto &name() const { return name_; }
+    int position() const { return position_; }
+    Type type() const { return type_; }
+    bool user_declared() const { return user_declared_; }
+    int token_position() const { return token_position_; }
+    cpp<#)
+  (:serialize (:slk)))
+
+(lcp:pop-namespace) ;; expr
+(lcp:pop-namespace) ;; memgraph
+
+#>cpp
+namespace std {
+
+template <>
+struct hash<memgraph::expr::Symbol> {
+  size_t operator()(const memgraph::expr::Symbol &symbol) const {
+    size_t prime = 265443599u;
+    size_t hash = std::hash<int>{}(symbol.position());
+    hash ^= prime * std::hash<std::string>{}(symbol.name());
+    hash ^= prime * std::hash<int>{}(static_cast<int>(symbol.type()));
+    return hash;
+  }
+};
+
+}  // namespace std
+
+cpp<#

src/expr/semantic/symbol_generator.hpp

@@ -0,0 +1,712 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+// Copyright 2017 Memgraph
+//
+// Created by Teon Banek on 11-03-2017
+
+#pragma once
+
+#include <algorithm>
+#include <optional>
+#include <ranges>
+#include <unordered_map>
+#include <unordered_set>
+#include <variant>
+#include <vector>
+
+#include "expr/ast.hpp"
+#include "expr/ast/ast_visitor.hpp"
+#include "expr/exceptions.hpp"
+#include "expr/semantic/symbol_table.hpp"
+
+namespace memgraph::expr {
+namespace detail {
+inline std::unordered_map<std::string, Identifier *> GeneratePredefinedIdentifierMap(
+    const std::vector<Identifier *> &predefined_identifiers) {
+  std::unordered_map<std::string, Identifier *> identifier_map;
+  for (const auto &identifier : predefined_identifiers) {
+    identifier_map.emplace(identifier->name_, identifier);
+  }
+
+  return identifier_map;
+}
+}  // namespace detail
+
+/// Visits the AST and generates symbols for variables.
+///
+/// During the process of symbol generation, simple semantic checks are
+/// performed. Such as, redeclaring a variable or conflicting expectations of
+/// variable types.
+class SymbolGenerator : public HierarchicalTreeVisitor {
+ public:
+  explicit SymbolGenerator(SymbolTable *symbol_table, const std::vector<Identifier *> &predefined_identifiers)
+      : symbol_table_(symbol_table),
+        predefined_identifiers_{detail::GeneratePredefinedIdentifierMap(predefined_identifiers)},
+        scopes_(1, Scope()) {}
+
+  using HierarchicalTreeVisitor::PostVisit;
+  using HierarchicalTreeVisitor::PreVisit;
+  using HierarchicalTreeVisitor::Visit;
+  using typename HierarchicalTreeVisitor::ReturnType;
+
+  // Query
+  bool PreVisit(SingleQuery & /*unused*/) override {
+    prev_return_names_ = curr_return_names_;
+    curr_return_names_.clear();
+    return true;
+  }
+
+  // Union
+  bool PreVisit(CypherUnion & /*unused*/) override {
+    scopes_.back() = Scope();
+    return true;
+  }
+
+  bool PostVisit(CypherUnion &cypher_union) override {
+    if (prev_return_names_ != curr_return_names_) {
+      throw SemanticException("All subqueries in an UNION must have the same column names.");
+    }
+
+    // create new symbols for the result of the union
+    for (const auto &name : curr_return_names_) {
+      auto symbol = CreateSymbol(name, false);
+      cypher_union.union_symbols_.push_back(symbol);
+    }
+
+    return true;
+  }
+
+  // Clauses
+  bool PreVisit(Create & /*unused*/) override {
+    scopes_.back().in_create = true;
+    return true;
+  }
+
+  bool PostVisit(Create & /*unused*/) override {
+    scopes_.back().in_create = false;
+    return true;
+  }
+
+  bool PreVisit(CallProcedure &call_proc) override {
+    for (auto *expr : call_proc.arguments_) {
+      expr->Accept(*this);
+    }
+    return false;
+  }
+
+  bool PostVisit(CallProcedure &call_proc) override {
+    for (auto *ident : call_proc.result_identifiers_) {
+      if (HasSymbolLocalScope(ident->name_)) {
+        throw RedeclareVariableError(ident->name_);
+      }
+      ident->MapTo(CreateSymbol(ident->name_, true));
+    }
+    return true;
+  }
+
+  bool PreVisit(LoadCsv & /*unused*/) override { return false; }
+
+  bool PostVisit(LoadCsv &load_csv) override {
+    if (HasSymbolLocalScope(load_csv.row_var_->name_)) {
+      throw RedeclareVariableError(load_csv.row_var_->name_);
+    }
+    load_csv.row_var_->MapTo(CreateSymbol(load_csv.row_var_->name_, true));
+    return true;
+  }
+
+  bool PreVisit(Return &ret) override {
+    auto &scope = scopes_.back();
+    scope.in_return = true;
+    VisitReturnBody(ret.body_);
+    scope.in_return = false;
+    return false;  // We handled the traversal ourselves.
+  }
+
+  bool PostVisit(Return & /*unused*/) override {
+    for (const auto &name_symbol : scopes_.back().symbols) curr_return_names_.insert(name_symbol.first);
+    return true;
+  }
+
+  bool PreVisit(With &with) override {
+    auto &scope = scopes_.back();
+    scope.in_with = true;
+    VisitReturnBody(with.body_, with.where_);
+    scope.in_with = false;
+    return false;  // We handled the traversal ourselves.
+  }
+
+  bool PreVisit(Where & /*unused*/) override {
+    scopes_.back().in_where = true;
+    return true;
+  }
+
+  bool PostVisit(Where & /*unused*/) override {
+    scopes_.back().in_where = false;
+    return true;
+  }
+
+  bool PreVisit(Merge & /*unused*/) override {
+    scopes_.back().in_merge = true;
+    return true;
+  }
+
+  bool PostVisit(Merge & /*unused*/) override {
+    scopes_.back().in_merge = false;
+    return true;
+  }
+
+  bool PostVisit(Unwind &unwind) override {
+    const auto &name = unwind.named_expression_->name_;
+    if (HasSymbolLocalScope(name)) {
+      throw RedeclareVariableError(name);
+    }
+    unwind.named_expression_->MapTo(CreateSymbol(name, true));
+    return true;
+  }
+
+  bool PreVisit(Match & /*unused*/) override {
+    scopes_.back().in_match = true;
+    return true;
+  }
+
+  bool PostVisit(Match & /*unused*/) override {
+    auto &scope = scopes_.back();
+    scope.in_match = false;
+    // Check variables in property maps after visiting Match, so that they can
+    // reference symbols out of bind order.
+    for (auto &ident : scope.identifiers_in_match) {
+      if (!HasSymbolLocalScope(ident->name_) && !ConsumePredefinedIdentifier(ident->name_))
+        throw UnboundVariableError(ident->name_);
+      ident->MapTo(scope.symbols[ident->name_]);
+    }
+    scope.identifiers_in_match.clear();
+    return true;
+  }
+
+  bool PreVisit(Foreach &for_each) override {
+    const auto &name = for_each.named_expression_->name_;
+    scopes_.emplace_back(Scope());
+    scopes_.back().in_foreach = true;
+    for_each.named_expression_->MapTo(
+        CreateSymbol(name, true, Symbol::Type::ANY, for_each.named_expression_->token_position_));
+    return true;
+  }
+
+  bool PostVisit(Foreach & /*unused*/) override {
+    scopes_.pop_back();
+    return true;
+  }
+
+  // Expressions
+  ReturnType Visit(Identifier &ident) override {
+    auto &scope = scopes_.back();
+    if (scope.in_skip || scope.in_limit) {
+      throw SemanticException("Variables are not allowed in {}.", scope.in_skip ? "SKIP" : "LIMIT");
+    }
+    Symbol symbol;
+    if (scope.in_pattern && !(scope.in_node_atom || scope.visiting_edge)) {
+      // If we are in the pattern, and outside of a node or an edge, the
+      // identifier is the pattern name.
+      symbol = GetOrCreateSymbolLocalScope(ident.name_, ident.user_declared_, Symbol::Type::PATH);
+    } else if (scope.in_pattern && scope.in_pattern_atom_identifier) {
+      //  Patterns used to create nodes and edges cannot redeclare already
+      //  established bindings. Declaration only happens in single node
+      //  patterns and in edge patterns. OpenCypher example,
+      //  `MATCH (n) CREATE (n)` should throw an error that `n` is already
+      //  declared. While `MATCH (n) CREATE (n) -[:R]-> (n)` is allowed,
+      //  since `n` now references the bound node instead of declaring it.
+      if ((scope.in_create_node || scope.in_create_edge) && HasSymbolLocalScope(ident.name_)) {
+        throw RedeclareVariableError(ident.name_);
+      }
+      auto type = Symbol::Type::VERTEX;
+      if (scope.visiting_edge) {
+        // Edge referencing is not allowed (like in Neo4j):
+        // `MATCH (n) - [r] -> (n) - [r] -> (n) RETURN r` is not allowed.
+        if (HasSymbolLocalScope(ident.name_)) {
+          throw RedeclareVariableError(ident.name_);
+        }
+        type = scope.visiting_edge->IsVariable() ? Symbol::Type::EDGE_LIST : Symbol::Type::EDGE;
+      }
+      symbol = GetOrCreateSymbolLocalScope(ident.name_, ident.user_declared_, type);
+    } else if (scope.in_pattern && !scope.in_pattern_atom_identifier && scope.in_match) {
+      if (scope.in_edge_range && scope.visiting_edge->identifier_->name_ == ident.name_) {
+        // Prevent variable path bounds to reference the identifier which is bound
+        // by the variable path itself.
+        throw UnboundVariableError(ident.name_);
+      }
+      // Variables in property maps or bounds of variable length path during MATCH
+      // can reference symbols bound later in the same MATCH. We collect them
+      // here, so that they can be checked after visiting Match.
+      scope.identifiers_in_match.emplace_back(&ident);
+    } else {
+      // Everything else references a bound symbol.
+      if (!HasSymbol(ident.name_) && !ConsumePredefinedIdentifier(ident.name_)) throw UnboundVariableError(ident.name_);
+      symbol = GetOrCreateSymbol(ident.name_, ident.user_declared_, Symbol::Type::ANY);
+    }
+    ident.MapTo(symbol);
+    return true;
+  }
+
+  ReturnType Visit(PrimitiveLiteral & /*unused*/) override { return true; }
+
+  ReturnType Visit(ParameterLookup & /*unused*/) override { return true; }
+
+  bool PreVisit(Aggregation &aggr) override {
+    auto &scope = scopes_.back();
+    // Check if the aggregation can be used in this context. This check should
+    // probably move to a separate phase, which checks if the query is well
+    // formed.
+    if ((!scope.in_return && !scope.in_with) || scope.in_order_by || scope.in_skip || scope.in_limit ||
+        scope.in_where) {
+      throw SemanticException("Aggregation functions are only allowed in WITH and RETURN.");
+    }
+    if (scope.in_aggregation) {
+      throw SemanticException(
+          "Using aggregation functions inside aggregation functions is not "
+          "allowed.");
+    }
+    if (scope.num_if_operators) {
+      // Neo allows aggregations here and produces very interesting behaviors.
+      // To simplify implementation at this moment we decided to completely
+      // disallow aggregations inside of the CASE.
+      // However, in some cases aggregation makes perfect sense, for example:
+      //    CASE count(n) WHEN 10 THEN "YES" ELSE "NO" END.
+      // TODO: Rethink of allowing aggregations in some parts of the CASE
+      // construct.
+      throw SemanticException("Using aggregation functions inside of CASE is not allowed.");
+    }
+    // Create a virtual symbol for aggregation result.
+    // Currently, we only have aggregation operators which return numbers.
+    auto aggr_name = Aggregation::OpToString(aggr.op_) + std::to_string(aggr.symbol_pos_);
+    aggr.MapTo(CreateSymbol(aggr_name, false, Symbol::Type::NUMBER));
+    scope.in_aggregation = true;
+    scope.has_aggregation = true;
+    return true;
+  }
+
+  bool PostVisit(Aggregation & /*unused*/) override {
+    scopes_.back().in_aggregation = false;
+    return true;
+  }
+
+  bool PreVisit(IfOperator & /*unused*/) override {
+    ++scopes_.back().num_if_operators;
+    return true;
+  }
+
+  bool PostVisit(IfOperator & /*unused*/) override {
+    --scopes_.back().num_if_operators;
+    return true;
+  }
+
+  bool PreVisit(All &all) override {
+    all.list_expression_->Accept(*this);
+    VisitWithIdentifiers(all.where_->expression_, {all.identifier_});
+    return false;
+  }
+
+  bool PreVisit(Single &single) override {
+    single.list_expression_->Accept(*this);
+    VisitWithIdentifiers(single.where_->expression_, {single.identifier_});
+    return false;
+  }
+
+  bool PreVisit(Any &any) override {
+    any.list_expression_->Accept(*this);
+    VisitWithIdentifiers(any.where_->expression_, {any.identifier_});
+    return false;
+  }
+
+  bool PreVisit(None &none) override {
+    none.list_expression_->Accept(*this);
+    VisitWithIdentifiers(none.where_->expression_, {none.identifier_});
+    return false;
+  }
+
+  bool PreVisit(Reduce &reduce) override {
+    reduce.initializer_->Accept(*this);
+    reduce.list_->Accept(*this);
+    VisitWithIdentifiers(reduce.expression_, {reduce.accumulator_, reduce.identifier_});
+    return false;
+  }
+
+  bool PreVisit(Extract &extract) override {
+    extract.list_->Accept(*this);
+    VisitWithIdentifiers(extract.expression_, {extract.identifier_});
+    return false;
+  }
+
+  // Pattern and its subparts.
+  bool PreVisit(Pattern &pattern) override {
+    auto &scope = scopes_.back();
+    scope.in_pattern = true;
+    if ((scope.in_create || scope.in_merge) && pattern.atoms_.size() == 1U) {
+      MG_ASSERT(utils::IsSubtype(*pattern.atoms_[0], NodeAtom::kType), "Expected a single NodeAtom in Pattern");
+      scope.in_create_node = true;
+    }
+    return true;
+  }
+
+  bool PostVisit(Pattern & /*unused*/) override {
+    auto &scope = scopes_.back();
+    scope.in_pattern = false;
+    scope.in_create_node = false;
+    return true;
+  }
+
+  bool PreVisit(NodeAtom &node_atom) override {
+    auto &scope = scopes_.back();
+    auto check_node_semantic = [&node_atom, &scope, this](const bool props_or_labels) {
+      const auto &node_name = node_atom.identifier_->name_;
+      if ((scope.in_create || scope.in_merge) && props_or_labels && HasSymbolLocalScope(node_name)) {
+        throw SemanticException("Cannot create node '" + node_name +
+                                "' with labels or properties, because it is already declared.");
+      }
+      scope.in_pattern_atom_identifier = true;
+      node_atom.identifier_->Accept(*this);
+      scope.in_pattern_atom_identifier = false;
+    };
+
+    scope.in_node_atom = true;
+    if (auto *properties = std::get_if<std::unordered_map<PropertyIx, Expression *>>(&node_atom.properties_)) {
+      bool props_or_labels = !properties->empty() || !node_atom.labels_.empty();
+
+      check_node_semantic(props_or_labels);
+      for (auto kv : *properties) {
+        kv.second->Accept(*this);
+      }
+
+      return false;
+    }
+    auto &properties_parameter = std::get<ParameterLookup *>(node_atom.properties_);
+    bool props_or_labels = !properties_parameter || !node_atom.labels_.empty();
+
+    check_node_semantic(props_or_labels);
+    properties_parameter->Accept(*this);
+    return false;
+  }
+
+  bool PostVisit(NodeAtom & /*unused*/) override {
+    scopes_.back().in_node_atom = false;
+    return true;
+  }
+
+  bool PreVisit(EdgeAtom &edge_atom) override {
+    auto &scope = scopes_.back();
+    scope.visiting_edge = &edge_atom;
+    if (scope.in_create || scope.in_merge) {
+      scope.in_create_edge = true;
+      if (edge_atom.edge_types_.size() != 1U) {
+        throw SemanticException(
+            "A single relationship type must be specified "
+            "when creating an edge.");
+      }
+      if (scope.in_create &&  // Merge allows bidirectionality
+          edge_atom.direction_ == EdgeAtom::Direction::BOTH) {
+        throw SemanticException(
+            "Bidirectional relationship are not supported "
+            "when creating an edge");
+      }
+      if (edge_atom.IsVariable()) {
+        throw SemanticException(
+            "Variable length relationships are not supported when creating an "
+            "edge.");
+      }
+    }
+    if (auto *properties = std::get_if<std::unordered_map<PropertyIx, Expression *>>(&edge_atom.properties_)) {
+      for (auto kv : *properties) {
+        kv.second->Accept(*this);
+      }
+    } else {
+      std::get<ParameterLookup *>(edge_atom.properties_)->Accept(*this);
+    }
+    if (edge_atom.IsVariable()) {
+      scope.in_edge_range = true;
+      if (edge_atom.lower_bound_) {
+        edge_atom.lower_bound_->Accept(*this);
+      }
+      if (edge_atom.upper_bound_) {
+        edge_atom.upper_bound_->Accept(*this);
+      }
+      scope.in_edge_range = false;
+      scope.in_pattern = false;
+      if (edge_atom.filter_lambda_.expression) {
+        VisitWithIdentifiers(edge_atom.filter_lambda_.expression,
+                             {edge_atom.filter_lambda_.inner_edge, edge_atom.filter_lambda_.inner_node});
+      } else {
+        // Create inner symbols, but don't bind them in scope, since they are to
+        // be used in the missing filter expression.
+        auto *inner_edge = edge_atom.filter_lambda_.inner_edge;
+        inner_edge->MapTo(
+            symbol_table_->CreateSymbol(inner_edge->name_, inner_edge->user_declared_, Symbol::Type::EDGE));
+        auto *inner_node = edge_atom.filter_lambda_.inner_node;
+        inner_node->MapTo(
+            symbol_table_->CreateSymbol(inner_node->name_, inner_node->user_declared_, Symbol::Type::VERTEX));
+      }
+      if (edge_atom.weight_lambda_.expression) {
+        VisitWithIdentifiers(edge_atom.weight_lambda_.expression,
+                             {edge_atom.weight_lambda_.inner_edge, edge_atom.weight_lambda_.inner_node});
+      }
+      scope.in_pattern = true;
+    }
+    scope.in_pattern_atom_identifier = true;
+    edge_atom.identifier_->Accept(*this);
+    scope.in_pattern_atom_identifier = false;
+    if (edge_atom.total_weight_) {
+      if (HasSymbolLocalScope(edge_atom.total_weight_->name_)) {
+        throw RedeclareVariableError(edge_atom.total_weight_->name_);
+      }
+      edge_atom.total_weight_->MapTo(GetOrCreateSymbolLocalScope(
+          edge_atom.total_weight_->name_, edge_atom.total_weight_->user_declared_, Symbol::Type::NUMBER));
+    }
+    return false;
+  }
+
+  bool PostVisit(EdgeAtom & /*unused*/) override {
+    auto &scope = scopes_.back();
+    scope.visiting_edge = nullptr;
+    scope.in_create_edge = false;
+    return true;
+  }
+
+ private:
+  // Scope stores the state of where we are when visiting the AST and a map of
+  // names to symbols.
+  struct Scope {
+    bool in_pattern{false};
+    bool in_merge{false};
+    bool in_create{false};
+    // in_create_node is true if we are creating or merging *only* a node.
+    // Therefore, it is *not* equivalent to (in_create || in_merge) &&
+    // in_node_atom.
+    bool in_create_node{false};
+    // True if creating an edge;
+    // shortcut for (in_create || in_merge) && visiting_edge.
+    bool in_create_edge{false};
+    bool in_node_atom{false};
+    EdgeAtom *visiting_edge{nullptr};
+    bool in_aggregation{false};
+    bool in_return{false};
+    bool in_with{false};
+    bool in_skip{false};
+    bool in_limit{false};
+    bool in_order_by{false};
+    bool in_where{false};
+    bool in_match{false};
+    bool in_foreach{false};
+    // True when visiting a pattern atom (node or edge) identifier, which can be
+    // reused or created in the pattern itself.
+    bool in_pattern_atom_identifier{false};
+    // True when visiting range bounds of a variable path.
+    bool in_edge_range{false};
+    // True if the return/with contains an aggregation in any named expression.
+    bool has_aggregation{false};
+    // Map from variable names to symbols.
+    std::map<std::string, Symbol> symbols;
+    // Identifiers found in property maps of patterns or as variable length path
+    // bounds in a single Match clause. They need to be checked after visiting
+    // Match. Identifiers created by naming vertices, edges and paths are *not*
+    // stored in here.
+    std::vector<Identifier *> identifiers_in_match;
+    // Number of nested IfOperators.
+    int num_if_operators{0};
+  };
+
+  inline static std::optional<Symbol> FindSymbolInScope(const std::string &name, const Scope &scope,
+                                                        Symbol::Type type) {
+    if (auto it = scope.symbols.find(name); it != scope.symbols.end()) {
+      const auto &symbol = it->second;
+      // Unless we have `ANY` type, check that types match.
+      if (type != Symbol::Type::ANY && symbol.type() != Symbol::Type::ANY && type != symbol.type()) {
+        throw TypeMismatchError(name, Symbol::TypeToString(symbol.type()), Symbol::TypeToString(type));
+      }
+      return symbol;
+    }
+    return std::nullopt;
+  }
+
+  bool HasSymbol(const std::string &name) const {
+    return std::ranges::any_of(scopes_, [&name](const auto &scope) { return scope.symbols.contains(name); });
+  }
+
+  bool HasSymbolLocalScope(const std::string &name) const { return scopes_.back().symbols.contains(name); }
+
+  // @return true if it added a predefined identifier with that name
+  bool ConsumePredefinedIdentifier(const std::string &name) {
+    auto it = predefined_identifiers_.find(name);
+
+    if (it == predefined_identifiers_.end()) {
+      return false;
+    }
+
+    // we can only use the predefined identifier in a single scope so we remove it after creating
+    // a symbol for it
+    auto &identifier = it->second;
+    MG_ASSERT(!identifier->user_declared_, "Predefined symbols cannot be user declared!");
+    identifier->MapTo(CreateSymbol(identifier->name_, identifier->user_declared_));
+    predefined_identifiers_.erase(it);
+    return true;
+  }
+
+  // Returns a freshly generated symbol. Previous mapping of the same name to a
+  // different symbol is replaced with the new one.
+  Symbol CreateSymbol(const std::string &name, bool user_declared, Symbol::Type type = Symbol::Type::ANY,
+                      int token_position = -1) {
+    auto symbol = symbol_table_->CreateSymbol(name, user_declared, type, token_position);
+    scopes_.back().symbols[name] = symbol;
+    return symbol;
+  }
+
+  Symbol GetOrCreateSymbol(const std::string &name, bool user_declared, Symbol::Type type = Symbol::Type::ANY) {
+    // NOLINTNEXTLINE
+    for (auto scope = scopes_.rbegin(); scope != scopes_.rend(); ++scope) {
+      if (auto maybe_symbol = FindSymbolInScope(name, *scope, type); maybe_symbol) {
+        return *maybe_symbol;
+      }
+    }
+    return CreateSymbol(name, user_declared, type);
+  }
+
+  // Returns the symbol by name. If the mapping already exists, checks if the
+  // types match. Otherwise, returns a new symbol.
+  Symbol GetOrCreateSymbolLocalScope(const std::string &name, bool user_declared,
+                                     Symbol::Type type = Symbol::Type::ANY) {
+    auto &scope = scopes_.back();
+    if (auto maybe_symbol = FindSymbolInScope(name, scope, type); maybe_symbol) {
+      return *maybe_symbol;
+    }
+    return CreateSymbol(name, user_declared, type);
+  }
+
+  void VisitReturnBody(ReturnBody &body, Where *where = nullptr) {
+    auto &scope = scopes_.back();
+    for (auto &expr : body.named_expressions) {
+      expr->Accept(*this);
+    }
+    std::vector<Symbol> user_symbols;
+    if (body.all_identifiers) {
+      // Carry over user symbols because '*' appeared.
+      for (const auto &sym_pair : scope.symbols) {
+        if (!sym_pair.second.user_declared()) {
+          continue;
+        }
+        user_symbols.emplace_back(sym_pair.second);
+      }
+      if (user_symbols.empty()) {
+        throw SemanticException("There are no variables in scope to use for '*'.");
+      }
+    }
+    // WITH/RETURN clause removes declarations of all the previous variables and
+    // declares only those established through named expressions. New declarations
+    // must not be visible inside named expressions themselves.
+    bool removed_old_names = false;
+    if ((!where && body.order_by.empty()) || scope.has_aggregation) {
+      // WHERE and ORDER BY need to see both the old and new symbols, unless we
+      // have an aggregation. Therefore, we can clear the symbols immediately if
+      // there is neither ORDER BY nor WHERE, or we have an aggregation.
+      scope.symbols.clear();
+      removed_old_names = true;
+    }
+    // Create symbols for named expressions.
+    std::unordered_set<std::string> new_names;
+    for (const auto &user_sym : user_symbols) {
+      new_names.insert(user_sym.name());
+      scope.symbols[user_sym.name()] = user_sym;
+    }
+    for (auto &named_expr : body.named_expressions) {
+      const auto &name = named_expr->name_;
+      if (!new_names.insert(name).second) {
+        throw SemanticException("Multiple results with the same name '{}' are not allowed.", name);
+      }
+      // An improvement would be to infer the type of the expression, so that the
+      // new symbol would have a more specific type.
+      named_expr->MapTo(CreateSymbol(name, true, Symbol::Type::ANY, named_expr->token_position_));
+    }
+    scope.in_order_by = true;
+    for (const auto &order_pair : body.order_by) {
+      order_pair.expression->Accept(*this);
+    }
+    scope.in_order_by = false;
+    if (body.skip) {
+      scope.in_skip = true;
+      body.skip->Accept(*this);
+      scope.in_skip = false;
+    }
+    if (body.limit) {
+      scope.in_limit = true;
+      body.limit->Accept(*this);
+      scope.in_limit = false;
+    }
+    if (where) where->Accept(*this);
+    if (!removed_old_names) {
+      // We have an ORDER BY or WHERE, but no aggregation, which means we didn't
+      // clear the old symbols, so do it now. We cannot just call clear, because
+      // we've added new symbols.
+      for (auto sym_it = scope.symbols.begin(); sym_it != scope.symbols.end();) {
+        if (new_names.find(sym_it->first) == new_names.end()) {
+          sym_it = scope.symbols.erase(sym_it);
+        } else {
+          sym_it++;
+        }
+      }
+    }
+    scopes_.back().has_aggregation = false;
+  }
+
+  void VisitWithIdentifiers(Expression *expr, const std::vector<Identifier *> &identifiers) {
+    auto &scope = scopes_.back();
+    std::vector<std::pair<std::optional<Symbol>, Identifier *>> prev_symbols;
+    // Collect previous symbols if they exist.
+    for (const auto &identifier : identifiers) {
+      std::optional<Symbol> prev_symbol;
+      auto prev_symbol_it = scope.symbols.find(identifier->name_);
+      if (prev_symbol_it != scope.symbols.end()) {
+        prev_symbol = prev_symbol_it->second;
+      }
+      identifier->MapTo(CreateSymbol(identifier->name_, identifier->user_declared_));
+      prev_symbols.emplace_back(prev_symbol, identifier);
+    }
+    // Visit the expression with the new symbols bound.
+    expr->Accept(*this);
+    // Restore back to previous symbols.
+    for (const auto &prev : prev_symbols) {
+      const auto &prev_symbol = prev.first;
+      const auto &identifier = prev.second;
+      if (prev_symbol) {
+        scope.symbols[identifier->name_] = *prev_symbol;
+      } else {
+        scope.symbols.erase(identifier->name_);
+      }
+    }
+  }
+
+  SymbolTable *symbol_table_;
+
+  // Identifiers which are injected from outside the query. Each identifier
+  // is mapped by its name.
+  std::unordered_map<std::string, Identifier *> predefined_identifiers_;
+  std::vector<Scope> scopes_;
+  std::unordered_set<std::string> prev_return_names_;
+  std::unordered_set<std::string> curr_return_names_;
+};
+
+inline SymbolTable MakeSymbolTable(CypherQuery *query, const std::vector<Identifier *> &predefined_identifiers = {}) {
+  SymbolTable symbol_table;
+  SymbolGenerator symbol_generator(&symbol_table, predefined_identifiers);
+  query->single_query_->Accept(symbol_generator);
+  for (auto *cypher_union : query->cypher_unions_) {
+    cypher_union->Accept(symbol_generator);
+  }
+  return symbol_table;
+}
+
+}  // namespace memgraph::expr

src/expr/semantic/symbol_table.hpp

@@ -0,0 +1,64 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <map>
+#include <string>
+
+#include "expr/ast.hpp"
+#include "expr/semantic/symbol.hpp"
+#include "utils/logging.hpp"
+
+namespace memgraph::expr {
+
+class SymbolTable final {
+ public:
+  SymbolTable() {}
+  const Symbol &CreateSymbol(const std::string &name, bool user_declared, Symbol::Type type = Symbol::Type::ANY,
+                             int32_t token_position = -1) {
+    MG_ASSERT(table_.size() <= std::numeric_limits<int32_t>::max(),
+              "SymbolTable size doesn't fit into 32-bit integer!");
+    auto got = table_.emplace(position_, Symbol(name, position_, user_declared, type, token_position));
+    MG_ASSERT(got.second, "Duplicate symbol ID!");
+    position_++;
+    return got.first->second;
+  }
+
+  // TODO(buda): This is the same logic as in the cypher_main_visitor. During
+  // parsing phase symbol table doesn't exist. Figure out a better solution.
+  const Symbol &CreateAnonymousSymbol(Symbol::Type type = Symbol::Type::ANY) {
+    int id = 1;
+    while (true) {
+      static const std::string &kAnonPrefix = "anon";
+      std::string name_candidate = kAnonPrefix + std::to_string(id++);
+      if (std::find_if(std::begin(table_), std::end(table_), [&name_candidate](const auto &item) -> bool {
+            return item.second.name_ == name_candidate;
+          }) == std::end(table_)) {
+        return CreateSymbol(name_candidate, false, type);
+      }
+    }
+  }
+
+  const Symbol &at(const Identifier &ident) const { return table_.at(ident.symbol_pos_); }
+  const Symbol &at(const NamedExpression &nexpr) const { return table_.at(nexpr.symbol_pos_); }
+  const Symbol &at(const Aggregation &aggr) const { return table_.at(aggr.symbol_pos_); }
+
+  // TODO: Remove these since members are public
+  int32_t max_position() const { return static_cast<int32_t>(table_.size()); }
+
+  const auto &table() const { return table_; }
+
+  int32_t position_{0};
+  std::map<int32_t, Symbol> table_;
+};
+
+}  // namespace memgraph::expr

src/glue/v2/auth.cpp

@@ -0,0 +1,64 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "glue/v2/auth.hpp"
+
+namespace memgraph::glue::v2 {
+
+auth::Permission PrivilegeToPermission(query::v2::AuthQuery::Privilege privilege) {
+  switch (privilege) {
+    case query::v2::AuthQuery::Privilege::MATCH:
+      return auth::Permission::MATCH;
+    case query::v2::AuthQuery::Privilege::CREATE:
+      return auth::Permission::CREATE;
+    case query::v2::AuthQuery::Privilege::MERGE:
+      return auth::Permission::MERGE;
+    case query::v2::AuthQuery::Privilege::DELETE:
+      return auth::Permission::DELETE;
+    case query::v2::AuthQuery::Privilege::SET:
+      return auth::Permission::SET;
+    case query::v2::AuthQuery::Privilege::REMOVE:
+      return auth::Permission::REMOVE;
+    case query::v2::AuthQuery::Privilege::INDEX:
+      return auth::Permission::INDEX;
+    case query::v2::AuthQuery::Privilege::STATS:
+      return auth::Permission::STATS;
+    case query::v2::AuthQuery::Privilege::CONSTRAINT:
+      return auth::Permission::CONSTRAINT;
+    case query::v2::AuthQuery::Privilege::DUMP:
+      return auth::Permission::DUMP;
+    case query::v2::AuthQuery::Privilege::REPLICATION:
+      return auth::Permission::REPLICATION;
+    case query::v2::AuthQuery::Privilege::DURABILITY:
+      return auth::Permission::DURABILITY;
+    case query::v2::AuthQuery::Privilege::READ_FILE:
+      return auth::Permission::READ_FILE;
+    case query::v2::AuthQuery::Privilege::FREE_MEMORY:
+      return auth::Permission::FREE_MEMORY;
+    case query::v2::AuthQuery::Privilege::TRIGGER:
+      return auth::Permission::TRIGGER;
+    case query::v2::AuthQuery::Privilege::CONFIG:
+      return auth::Permission::CONFIG;
+    case query::v2::AuthQuery::Privilege::AUTH:
+      return auth::Permission::AUTH;
+    case query::v2::AuthQuery::Privilege::STREAM:
+      return auth::Permission::STREAM;
+    case query::v2::AuthQuery::Privilege::MODULE_READ:
+      return auth::Permission::MODULE_READ;
+    case query::v2::AuthQuery::Privilege::MODULE_WRITE:
+      return auth::Permission::MODULE_WRITE;
+    case query::v2::AuthQuery::Privilege::WEBSOCKET:
+      return auth::Permission::WEBSOCKET;
+    case query::v2::AuthQuery::Privilege::SCHEMA:
+      return auth::Permission::SCHEMA;
+  }
+}
+}  // namespace memgraph::glue::v2

src/glue/v2/auth.hpp

@@ -0,0 +1,23 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "auth/models.hpp"
+#include "query/v2/frontend/ast/ast.hpp"
+
+namespace memgraph::glue::v2 {
+
+/**
+ * This function converts query::AuthQuery::Privilege to its corresponding
+ * auth::Permission.
+ */
+auth::Permission PrivilegeToPermission(query::v2::AuthQuery::Privilege privilege);
+
+}  // namespace memgraph::glue::v2

src/glue/v2/communication.cpp

@@ -0,0 +1,277 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "glue/v2/communication.hpp"
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "storage/v3/edge_accessor.hpp"
+#include "storage/v3/shard.hpp"
+#include "storage/v3/vertex_accessor.hpp"
+#include "utils/temporal.hpp"
+
+using memgraph::communication::bolt::Value;
+
+namespace memgraph::glue::v2 {
+
+query::v2::TypedValue ToTypedValue(const Value &value) {
+  switch (value.type()) {
+    case Value::Type::Null:
+      return {};
+    case Value::Type::Bool:
+      return query::v2::TypedValue(value.ValueBool());
+    case Value::Type::Int:
+      return query::v2::TypedValue(value.ValueInt());
+    case Value::Type::Double:
+      return query::v2::TypedValue(value.ValueDouble());
+    case Value::Type::String:
+      return query::v2::TypedValue(value.ValueString());
+    case Value::Type::List: {
+      std::vector<query::v2::TypedValue> list;
+      list.reserve(value.ValueList().size());
+      for (const auto &v : value.ValueList()) list.push_back(ToTypedValue(v));
+      return query::v2::TypedValue(std::move(list));
+    }
+    case Value::Type::Map: {
+      std::map<std::string, query::v2::TypedValue> map;
+      for (const auto &kv : value.ValueMap()) map.emplace(kv.first, ToTypedValue(kv.second));
+      return query::v2::TypedValue(std::move(map));
+    }
+    case Value::Type::Vertex:
+    case Value::Type::Edge:
+    case Value::Type::UnboundedEdge:
+    case Value::Type::Path:
+      throw communication::bolt::ValueException("Unsupported conversion from Value to TypedValue");
+    case Value::Type::Date:
+      return query::v2::TypedValue(value.ValueDate());
+    case Value::Type::LocalTime:
+      return query::v2::TypedValue(value.ValueLocalTime());
+    case Value::Type::LocalDateTime:
+      return query::v2::TypedValue(value.ValueLocalDateTime());
+    case Value::Type::Duration:
+      return query::v2::TypedValue(value.ValueDuration());
+  }
+}
+
+storage::v3::Result<communication::bolt::Vertex> ToBoltVertex(const query::v2::VertexAccessor &vertex,
+                                                              const storage::v3::Shard &db, storage::v3::View view) {
+  return ToBoltVertex(vertex.impl_, db, view);
+}
+
+storage::v3::Result<communication::bolt::Edge> ToBoltEdge(const query::v2::EdgeAccessor &edge,
+                                                          const storage::v3::Shard &db, storage::v3::View view) {
+  return ToBoltEdge(edge.impl_, db, view);
+}
+
+storage::v3::Result<Value> ToBoltValue(const query::v2::TypedValue &value, const storage::v3::Shard &db,
+                                       storage::v3::View view) {
+  switch (value.type()) {
+    case query::v2::TypedValue::Type::Null:
+      return Value();
+    case query::v2::TypedValue::Type::Bool:
+      return Value(value.ValueBool());
+    case query::v2::TypedValue::Type::Int:
+      return Value(value.ValueInt());
+    case query::v2::TypedValue::Type::Double:
+      return Value(value.ValueDouble());
+    case query::v2::TypedValue::Type::String:
+      return Value(std::string(value.ValueString()));
+    case query::v2::TypedValue::Type::List: {
+      std::vector<Value> values;
+      values.reserve(value.ValueList().size());
+      for (const auto &v : value.ValueList()) {
+        auto maybe_value = ToBoltValue(v, db, view);
+        if (maybe_value.HasError()) return maybe_value.GetError();
+        values.emplace_back(std::move(*maybe_value));
+      }
+      return Value(std::move(values));
+    }
+    case query::v2::TypedValue::Type::Map: {
+      std::map<std::string, Value> map;
+      for (const auto &kv : value.ValueMap()) {
+        auto maybe_value = ToBoltValue(kv.second, db, view);
+        if (maybe_value.HasError()) return maybe_value.GetError();
+        map.emplace(kv.first, std::move(*maybe_value));
+      }
+      return Value(std::move(map));
+    }
+    case query::v2::TypedValue::Type::Vertex: {
+      auto maybe_vertex = ToBoltVertex(value.ValueVertex(), db, view);
+      if (maybe_vertex.HasError()) return maybe_vertex.GetError();
+      return Value(std::move(*maybe_vertex));
+    }
+    case query::v2::TypedValue::Type::Edge: {
+      auto maybe_edge = ToBoltEdge(value.ValueEdge(), db, view);
+      if (maybe_edge.HasError()) return maybe_edge.GetError();
+      return Value(std::move(*maybe_edge));
+    }
+    case query::v2::TypedValue::Type::Path: {
+      auto maybe_path = ToBoltPath(value.ValuePath(), db, view);
+      if (maybe_path.HasError()) return maybe_path.GetError();
+      return Value(std::move(*maybe_path));
+    }
+    case query::v2::TypedValue::Type::Date:
+      return Value(value.ValueDate());
+    case query::v2::TypedValue::Type::LocalTime:
+      return Value(value.ValueLocalTime());
+    case query::v2::TypedValue::Type::LocalDateTime:
+      return Value(value.ValueLocalDateTime());
+    case query::v2::TypedValue::Type::Duration:
+      return Value(value.ValueDuration());
+  }
+}
+
+storage::v3::Result<communication::bolt::Vertex> ToBoltVertex(const storage::v3::VertexAccessor &vertex,
+                                                              const storage::v3::Shard &db, storage::v3::View view) {
+  // TODO(jbajic) Fix bolt communication
+  auto id = communication::bolt::Id::FromUint(0);
+  auto maybe_labels = vertex.Labels(view);
+  if (maybe_labels.HasError()) return maybe_labels.GetError();
+  std::vector<std::string> labels;
+  labels.reserve(maybe_labels->size());
+  for (const auto &label : *maybe_labels) {
+    labels.push_back(db.LabelToName(label));
+  }
+  auto maybe_properties = vertex.Properties(view);
+  if (maybe_properties.HasError()) return maybe_properties.GetError();
+  std::map<std::string, Value> properties;
+  for (const auto &prop : *maybe_properties) {
+    properties[db.PropertyToName(prop.first)] = ToBoltValue(prop.second);
+  }
+  return communication::bolt::Vertex{id, labels, properties};
+}
+
+storage::v3::Result<communication::bolt::Edge> ToBoltEdge(const storage::v3::EdgeAccessor &edge,
+                                                          const storage::v3::Shard &db, storage::v3::View view) {
+  // TODO(jbajic) Fix bolt communication
+  auto id = communication::bolt::Id::FromUint(0);
+  auto from = communication::bolt::Id::FromUint(0);
+  auto to = communication::bolt::Id::FromUint(0);
+  const auto &type = db.EdgeTypeToName(edge.EdgeType());
+  auto maybe_properties = edge.Properties(view);
+  if (maybe_properties.HasError()) return maybe_properties.GetError();
+  std::map<std::string, Value> properties;
+  for (const auto &prop : *maybe_properties) {
+    properties[db.PropertyToName(prop.first)] = ToBoltValue(prop.second);
+  }
+  return communication::bolt::Edge{id, from, to, type, properties};
+}
+
+storage::v3::Result<communication::bolt::Path> ToBoltPath(const query::v2::Path &path, const storage::v3::Shard &db,
+                                                          storage::v3::View view) {
+  std::vector<communication::bolt::Vertex> vertices;
+  vertices.reserve(path.vertices().size());
+  for (const auto &v : path.vertices()) {
+    auto maybe_vertex = ToBoltVertex(v, db, view);
+    if (maybe_vertex.HasError()) return maybe_vertex.GetError();
+    vertices.emplace_back(std::move(*maybe_vertex));
+  }
+  std::vector<communication::bolt::Edge> edges;
+  edges.reserve(path.edges().size());
+  for (const auto &e : path.edges()) {
+    auto maybe_edge = ToBoltEdge(e, db, view);
+    if (maybe_edge.HasError()) return maybe_edge.GetError();
+    edges.emplace_back(std::move(*maybe_edge));
+  }
+  return communication::bolt::Path(vertices, edges);
+}
+
+storage::v3::PropertyValue ToPropertyValue(const Value &value) {
+  switch (value.type()) {
+    case Value::Type::Null:
+      return {};
+    case Value::Type::Bool:
+      return storage::v3::PropertyValue(value.ValueBool());
+    case Value::Type::Int:
+      return storage::v3::PropertyValue(value.ValueInt());
+    case Value::Type::Double:
+      return storage::v3::PropertyValue(value.ValueDouble());
+    case Value::Type::String:
+      return storage::v3::PropertyValue(value.ValueString());
+    case Value::Type::List: {
+      std::vector<storage::v3::PropertyValue> vec;
+      vec.reserve(value.ValueList().size());
+      for (const auto &value : value.ValueList()) vec.emplace_back(ToPropertyValue(value));
+      return storage::v3::PropertyValue(std::move(vec));
+    }
+    case Value::Type::Map: {
+      std::map<std::string, storage::v3::PropertyValue> map;
+      for (const auto &kv : value.ValueMap()) map.emplace(kv.first, ToPropertyValue(kv.second));
+      return storage::v3::PropertyValue(std::move(map));
+    }
+    case Value::Type::Vertex:
+    case Value::Type::Edge:
+    case Value::Type::UnboundedEdge:
+    case Value::Type::Path:
+      throw communication::bolt::ValueException("Unsupported conversion from Value to PropertyValue");
+    case Value::Type::Date:
+      return storage::v3::PropertyValue(
+          storage::v3::TemporalData(storage::v3::TemporalType::Date, value.ValueDate().MicrosecondsSinceEpoch()));
+    case Value::Type::LocalTime:
+      return storage::v3::PropertyValue(storage::v3::TemporalData(storage::v3::TemporalType::LocalTime,
+                                                                  value.ValueLocalTime().MicrosecondsSinceEpoch()));
+    case Value::Type::LocalDateTime:
+      return storage::v3::PropertyValue(storage::v3::TemporalData(storage::v3::TemporalType::LocalDateTime,
+                                                                  value.ValueLocalDateTime().MicrosecondsSinceEpoch()));
+    case Value::Type::Duration:
+      return storage::v3::PropertyValue(
+          storage::v3::TemporalData(storage::v3::TemporalType::Duration, value.ValueDuration().microseconds));
+  }
+}
+
+Value ToBoltValue(const storage::v3::PropertyValue &value) {
+  switch (value.type()) {
+    case storage::v3::PropertyValue::Type::Null:
+      return {};
+    case storage::v3::PropertyValue::Type::Bool:
+      return {value.ValueBool()};
+    case storage::v3::PropertyValue::Type::Int:
+      return {value.ValueInt()};
+      break;
+    case storage::v3::PropertyValue::Type::Double:
+      return {value.ValueDouble()};
+    case storage::v3::PropertyValue::Type::String:
+      return {value.ValueString()};
+    case storage::v3::PropertyValue::Type::List: {
+      const auto &values = value.ValueList();
+      std::vector<Value> vec;
+      vec.reserve(values.size());
+      for (const auto &v : values) {
+        vec.push_back(ToBoltValue(v));
+      }
+      return {std::move(vec)};
+    }
+    case storage::v3::PropertyValue::Type::Map: {
+      const auto &map = value.ValueMap();
+      std::map<std::string, Value> dv_map;
+      for (const auto &kv : map) {
+        dv_map.emplace(kv.first, ToBoltValue(kv.second));
+      }
+      return {std::move(dv_map)};
+    }
+    case storage::v3::PropertyValue::Type::TemporalData:
+      const auto &type = value.ValueTemporalData();
+      switch (type.type) {
+        case storage::v3::TemporalType::Date:
+          return {utils::Date(type.microseconds)};
+        case storage::v3::TemporalType::LocalTime:
+          return {utils::LocalTime(type.microseconds)};
+        case storage::v3::TemporalType::LocalDateTime:
+          return {utils::LocalDateTime(type.microseconds)};
+        case storage::v3::TemporalType::Duration:
+          return {utils::Duration(type.microseconds)};
+      }
+  }
+}
+
+}  // namespace memgraph::glue::v2

src/glue/v2/communication.hpp

@@ -0,0 +1,68 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+/// @file Conversion functions between Value and other memgraph types.
+#pragma once
+
+#include "communication/bolt/v1/value.hpp"
+#include "query/v2/bindings/typed_value.hpp"
+#include "storage/v3/property_value.hpp"
+#include "storage/v3/result.hpp"
+#include "storage/v3/view.hpp"
+
+namespace memgraph::storage::v3 {
+class EdgeAccessor;
+class Storage;
+class VertexAccessor;
+}  // namespace memgraph::storage::v3
+
+namespace memgraph::glue::v2 {
+
+/// @param storage::v3::VertexAccessor for converting to
+///        communication::bolt::Vertex.
+/// @param storage::v3::Shard for getting label and property names.
+/// @param storage::v3::View for deciding which vertex attributes are visible.
+///
+/// @throw std::bad_alloc
+storage::v3::Result<communication::bolt::Vertex> ToBoltVertex(const storage::v3::VertexAccessor &vertex,
+                                                              const storage::v3::Shard &db, storage::v3::View view);
+
+/// @param storage::v3::EdgeAccessor for converting to communication::bolt::Edge.
+/// @param storage::v3::Shard for getting edge type and property names.
+/// @param storage::v3::View for deciding which edge attributes are visible.
+///
+/// @throw std::bad_alloc
+storage::v3::Result<communication::bolt::Edge> ToBoltEdge(const storage::v3::EdgeAccessor &edge,
+                                                          const storage::v3::Shard &db, storage::v3::View view);
+
+/// @param query::v2::Path for converting to communication::bolt::Path.
+/// @param storage::v3::Shard for ToBoltVertex and ToBoltEdge.
+/// @param storage::v3::View for ToBoltVertex and ToBoltEdge.
+///
+/// @throw std::bad_alloc
+storage::v3::Result<communication::bolt::Path> ToBoltPath(const query::v2::Path &path, const storage::v3::Shard &db,
+                                                          storage::v3::View view);
+
+/// @param query::v2::TypedValue for converting to communication::bolt::Value.
+/// @param storage::v3::Shard for ToBoltVertex and ToBoltEdge.
+/// @param storage::v3::View for ToBoltVertex and ToBoltEdge.
+///
+/// @throw std::bad_alloc
+storage::v3::Result<communication::bolt::Value> ToBoltValue(const query::v2::TypedValue &value,
+                                                            const storage::v3::Shard &db, storage::v3::View view);
+
+query::v2::TypedValue ToTypedValue(const communication::bolt::Value &value);
+
+communication::bolt::Value ToBoltValue(const storage::v3::PropertyValue &value);
+
+storage::v3::PropertyValue ToPropertyValue(const communication::bolt::Value &value);
+
+}  // namespace memgraph::glue::v2

src/io/address.hpp

@@ -0,0 +1,77 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <compare>
+
+#include <fmt/format.h>
+#include <boost/asio/ip/tcp.hpp>
+#include <boost/uuid/uuid.hpp>
+#include <boost/uuid/uuid_generators.hpp>
+#include <boost/uuid/uuid_io.hpp>
+
+namespace memgraph::io {
+struct Address {
+  // It's important for all participants to have a
+  // unique identifier - IP and port alone are not
+  // enough, and may change over the lifecycle of
+  // the nodes. Particularly storage nodes may change
+  // their IP addresses over time, and the system
+  // should gracefully update its information
+  // about them.
+  boost::uuids::uuid unique_id;
+  boost::asio::ip::address last_known_ip;
+  uint16_t last_known_port;
+
+  static Address TestAddress(uint16_t port) {
+    return Address{
+        .unique_id = boost::uuids::uuid{boost::uuids::random_generator()()},
+        .last_known_port = port,
+    };
+  }
+
+  static Address UniqueLocalAddress() {
+    return Address{
+        .unique_id = boost::uuids::uuid{boost::uuids::random_generator()()},
+    };
+  }
+
+  /// Returns a new ID with the same IP and port but a unique UUID.
+  Address ForkUniqueAddress() {
+    return Address{
+        .unique_id = boost::uuids::uuid{boost::uuids::random_generator()()},
+        .last_known_ip = last_known_ip,
+        .last_known_port = last_known_port,
+    };
+  }
+
+  friend bool operator==(const Address &lhs, const Address &rhs) = default;
+
+  /// unique_id is most dominant for ordering, then last_known_ip, then last_known_port
+  friend bool operator<(const Address &lhs, const Address &rhs) {
+    if (lhs.unique_id != rhs.unique_id) {
+      return lhs.unique_id < rhs.unique_id;
+    }
+
+    if (lhs.last_known_ip != rhs.last_known_ip) {
+      return lhs.last_known_ip < rhs.last_known_ip;
+    }
+
+    return lhs.last_known_port < rhs.last_known_port;
+  }
+
+  std::string ToString() const {
+    return fmt::format("Address {{ unique_id: {}, last_known_ip: {}, last_known_port: {} }}",
+                       boost::uuids::to_string(unique_id), last_known_ip.to_string(), last_known_port);
+  }
+};
+};  // namespace memgraph::io

src/io/errors.hpp

@@ -0,0 +1,26 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+namespace memgraph::io {
+// Signifies that a retriable operation was unable to
+// complete after a configured number of retries.
+struct RetriesExhausted {};
+
+// Signifies that a request was unable to receive a response
+// within some configured timeout duration. It is important
+// to remember that in distributed systems, a timeout does
+// not signify that a request was not received or processed.
+// It may be the case that the request was fully processed
+// but that the response was not received.
+struct TimedOut {};
+};  // namespace memgraph::io

src/io/future.hpp

@@ -0,0 +1,256 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <thread>
+#include <utility>
+
+#include "io/errors.hpp"
+#include "utils/logging.hpp"
+
+namespace memgraph::io {
+
+// Shared is in an anonymous namespace, and the only way to
+// construct a Promise or Future is to pass a Shared in. This
+// ensures that Promises and Futures can only be constructed
+// in this translation unit.
+namespace details {
+template <typename T>
+class Shared {
+  mutable std::condition_variable cv_;
+  mutable std::mutex mu_;
+  std::optional<T> item_;
+  bool consumed_ = false;
+  bool waiting_ = false;
+  std::function<bool()> simulator_notifier_ = nullptr;
+
+ public:
+  explicit Shared(std::function<bool()> simulator_notifier) : simulator_notifier_(simulator_notifier) {}
+  Shared() = default;
+  Shared(Shared &&) = delete;
+  Shared &operator=(Shared &&) = delete;
+  Shared(const Shared &) = delete;
+  Shared &operator=(const Shared &) = delete;
+  ~Shared() = default;
+
+  /// Takes the item out of our optional item_ and returns it.
+  T Take() {
+    MG_ASSERT(item_, "Take called without item_ being present");
+    MG_ASSERT(!consumed_, "Take called on already-consumed Future");
+
+    T ret = std::move(item_).value();
+    item_.reset();
+
+    consumed_ = true;
+
+    return ret;
+  }
+
+  T Wait() {
+    std::unique_lock<std::mutex> lock(mu_);
+    waiting_ = true;
+
+    while (!item_) {
+      bool simulator_progressed = false;
+      if (simulator_notifier_) [[unlikely]] {
+        // We can't hold our own lock while notifying
+        // the simulator because notifying the simulator
+        // involves acquiring the simulator's mutex
+        // to guarantee that our notification linearizes
+        // with the simulator's condition variable.
+        // However, the simulator may acquire our
+        // mutex to check if we are being awaited,
+        // while determining system quiescence,
+        // so we have to get out of its way to avoid
+        // a cyclical deadlock.
+        lock.unlock();
+        simulator_progressed = std::invoke(simulator_notifier_);
+        lock.lock();
+        if (item_) {
+          // item may have been filled while we
+          // had dropped our mutex while notifying
+          // the simulator of our waiting_ status.
+          break;
+        }
+      }
+      if (!simulator_progressed) [[likely]] {
+        cv_.wait(lock);
+      }
+      MG_ASSERT(!consumed_, "Future consumed twice!");
+    }
+
+    waiting_ = false;
+
+    return Take();
+  }
+
+  bool IsReady() const {
+    std::unique_lock<std::mutex> lock(mu_);
+    return item_.has_value();
+  }
+
+  std::optional<T> TryGet() {
+    std::unique_lock<std::mutex> lock(mu_);
+
+    if (item_) {
+      return Take();
+    }
+
+    return std::nullopt;
+  }
+
+  void Fill(T item) {
+    {
+      std::unique_lock<std::mutex> lock(mu_);
+
+      MG_ASSERT(!consumed_, "Promise filled after it was already consumed!");
+      MG_ASSERT(!item_, "Promise filled twice!");
+
+      item_ = item;
+    }  // lock released before condition variable notification
+
+    cv_.notify_all();
+  }
+
+  bool IsAwaited() const {
+    std::unique_lock<std::mutex> lock(mu_);
+    return waiting_;
+  }
+};
+}  // namespace details
+
+template <typename T>
+class Future {
+  bool consumed_or_moved_ = false;
+  std::shared_ptr<details::Shared<T>> shared_;
+
+ public:
+  explicit Future(std::shared_ptr<details::Shared<T>> shared) : shared_(shared) {}
+
+  Future() = delete;
+  Future(Future &&old) noexcept {
+    MG_ASSERT(!old.consumed_or_moved_, "Future moved from after already being moved from or consumed.");
+    shared_ = std::move(old.shared_);
+    consumed_or_moved_ = old.consumed_or_moved_;
+    old.consumed_or_moved_ = true;
+  }
+
+  Future(const Future &) = delete;
+  Future &operator=(const Future &) = delete;
+  ~Future() = default;
+
+  /// Returns true if the Future is ready to
+  /// be consumed using TryGet or Wait (prefer Wait
+  /// if you know it's ready, because it doesn't
+  /// return an optional.
+  bool IsReady() {
+    MG_ASSERT(!consumed_or_moved_, "Called IsReady after Future already consumed!");
+    return shared_->IsReady();
+  }
+
+  /// Non-blocking method that returns the inner
+  /// item if it's already ready, or std::nullopt
+  /// if it is not ready yet.
+  std::optional<T> TryGet() {
+    MG_ASSERT(!consumed_or_moved_, "Called TryGet after Future already consumed!");
+    std::optional<T> ret = shared_->TryGet();
+    if (ret) {
+      consumed_or_moved_ = true;
+    }
+    return ret;
+  }
+
+  /// Block on the corresponding promise to be filled,
+  /// returning the inner item when ready.
+  T Wait() && {
+    MG_ASSERT(!consumed_or_moved_, "Future should only be consumed with Wait once!");
+    T ret = shared_->Wait();
+    consumed_or_moved_ = true;
+    return ret;
+  }
+
+  /// Marks this Future as canceled.
+  void Cancel() {
+    MG_ASSERT(!consumed_or_moved_, "Future::Cancel called on a future that was already moved or consumed!");
+    consumed_or_moved_ = true;
+  }
+};
+
+template <typename T>
+class Promise {
+  std::shared_ptr<details::Shared<T>> shared_;
+  bool filled_or_moved_ = false;
+
+ public:
+  explicit Promise(std::shared_ptr<details::Shared<T>> shared) : shared_(shared) {}
+
+  Promise() = delete;
+  Promise(Promise &&old) noexcept {
+    MG_ASSERT(!old.filled_or_moved_, "Promise moved from after already being moved from or filled.");
+    shared_ = std::move(old.shared_);
+    old.filled_or_moved_ = true;
+  }
+
+  Promise &operator=(Promise &&old) noexcept {
+    MG_ASSERT(!old.filled_or_moved_, "Promise moved from after already being moved from or filled.");
+    shared_ = std::move(old.shared_);
+    old.filled_or_moved_ = true;
+  }
+  Promise(const Promise &) = delete;
+  Promise &operator=(const Promise &) = delete;
+
+  ~Promise() { MG_ASSERT(filled_or_moved_, "Promise destroyed before its associated Future was filled!"); }
+
+  // Fill the expected item into the Future.
+  void Fill(T item) {
+    MG_ASSERT(!filled_or_moved_, "Promise::Fill called on a promise that is already filled or moved!");
+    shared_->Fill(item);
+    filled_or_moved_ = true;
+  }
+
+  bool IsAwaited() { return shared_->IsAwaited(); }
+
+  /// Moves this Promise into a unique_ptr.
+  std::unique_ptr<Promise<T>> ToUnique() && {
+    std::unique_ptr<Promise<T>> up = std::make_unique<Promise<T>>(std::move(shared_));
+
+    filled_or_moved_ = true;
+
+    return up;
+  }
+};
+
+template <typename T>
+std::pair<Future<T>, Promise<T>> FuturePromisePair() {
+  std::shared_ptr<details::Shared<T>> shared = std::make_shared<details::Shared<T>>();
+
+  Future<T> future = Future<T>(shared);
+  Promise<T> promise = Promise<T>(shared);
+
+  return std::make_pair(std::move(future), std::move(promise));
+}
+
+template <typename T>
+std::pair<Future<T>, Promise<T>> FuturePromisePairWithNotifier(std::function<bool()> simulator_notifier) {
+  std::shared_ptr<details::Shared<T>> shared = std::make_shared<details::Shared<T>>(simulator_notifier);
+
+  Future<T> future = Future<T>(shared);
+  Promise<T> promise = Promise<T>(shared);
+
+  return std::make_pair(std::move(future), std::move(promise));
+}
+
+};  // namespace memgraph::io

src/io/local_transport/local_system.hpp

@@ -0,0 +1,35 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <random>
+
+#include "io/address.hpp"
+#include "io/local_transport/local_transport.hpp"
+#include "io/local_transport/local_transport_handle.hpp"
+#include "io/transport.hpp"
+
+namespace memgraph::io::local_transport {
+
+class LocalSystem {
+  std::shared_ptr<LocalTransportHandle> local_transport_handle_ = std::make_shared<LocalTransportHandle>();
+
+ public:
+  Io<LocalTransport> Register(Address address) {
+    LocalTransport local_transport(local_transport_handle_);
+    return Io{local_transport, address};
+  }
+
+  void ShutDown() { local_transport_handle_->ShutDown(); }
+};
+
+}  // namespace memgraph::io::local_transport

src/io/local_transport/local_transport.hpp

@@ -0,0 +1,64 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <chrono>
+#include <memory>
+#include <random>
+#include <utility>
+
+#include "io/address.hpp"
+#include "io/local_transport/local_transport_handle.hpp"
+#include "io/time.hpp"
+#include "io/transport.hpp"
+
+namespace memgraph::io::local_transport {
+
+class LocalTransport {
+  std::shared_ptr<LocalTransportHandle> local_transport_handle_;
+
+ public:
+  explicit LocalTransport(std::shared_ptr<LocalTransportHandle> local_transport_handle)
+      : local_transport_handle_(std::move(local_transport_handle)) {}
+
+  template <Message RequestT, Message ResponseT>
+  ResponseFuture<ResponseT> Request(Address to_address, Address from_address, RequestId request_id, RequestT request,
+                                    Duration timeout) {
+    auto [future, promise] = memgraph::io::FuturePromisePair<ResponseResult<ResponseT>>();
+
+    local_transport_handle_->SubmitRequest(to_address, from_address, request_id, std::move(request), timeout,
+                                           std::move(promise));
+
+    return std::move(future);
+  }
+
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) RequestResult<Ms...> Receive(Address receiver_address, Duration timeout) {
+    return local_transport_handle_->template Receive<Ms...>(receiver_address, timeout);
+  }
+
+  template <Message M>
+  void Send(Address to_address, Address from_address, RequestId request_id, M &&message) {
+    return local_transport_handle_->template Send<M>(to_address, from_address, request_id, std::forward<M>(message));
+  }
+
+  Time Now() const { return local_transport_handle_->Now(); }
+
+  bool ShouldShutDown() const { return local_transport_handle_->ShouldShutDown(); }
+
+  template <class D = std::poisson_distribution<>, class Return = uint64_t>
+  Return Rand(D distrib) {
+    std::random_device rng;
+    return distrib(rng);
+  }
+};
+};  // namespace memgraph::io::local_transport

src/io/local_transport/local_transport_handle.hpp

@@ -0,0 +1,151 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <chrono>
+#include <condition_variable>
+#include <iostream>
+#include <map>
+#include <mutex>
+
+#include "io/errors.hpp"
+#include "io/message_conversion.hpp"
+#include "io/time.hpp"
+#include "io/transport.hpp"
+
+namespace memgraph::io::local_transport {
+
+class LocalTransportHandle {
+  mutable std::mutex mu_{};
+  mutable std::condition_variable cv_;
+  bool should_shut_down_ = false;
+
+  // the responses to requests that are being waited on
+  std::map<PromiseKey, DeadlineAndOpaquePromise> promises_;
+
+  // messages that are sent to servers that may later receive them
+  std::vector<OpaqueMessage> can_receive_;
+
+ public:
+  ~LocalTransportHandle() {
+    for (auto &&[pk, promise] : promises_) {
+      std::move(promise.promise).TimeOut();
+    }
+    promises_.clear();
+  }
+
+  void ShutDown() {
+    std::unique_lock<std::mutex> lock(mu_);
+    should_shut_down_ = true;
+    cv_.notify_all();
+  }
+
+  bool ShouldShutDown() const {
+    std::unique_lock<std::mutex> lock(mu_);
+    return should_shut_down_;
+  }
+
+  static Time Now() {
+    auto nano_time = std::chrono::system_clock::now();
+    return std::chrono::time_point_cast<std::chrono::microseconds>(nano_time);
+  }
+
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) RequestResult<Ms...> Receive(Address /* receiver_address */, Duration timeout) {
+    std::unique_lock lock(mu_);
+
+    Time before = Now();
+
+    spdlog::info("can_receive_ size: {}", can_receive_.size());
+
+    while (can_receive_.empty()) {
+      Time now = Now();
+
+      // protection against non-monotonic timesources
+      auto maxed_now = std::max(now, before);
+      auto elapsed = maxed_now - before;
+
+      if (timeout < elapsed) {
+        return TimedOut{};
+      }
+
+      Duration relative_timeout = timeout - elapsed;
+
+      std::cv_status cv_status_value = cv_.wait_for(lock, relative_timeout);
+
+      if (cv_status_value == std::cv_status::timeout) {
+        return TimedOut{};
+      }
+    }
+
+    auto current_message = std::move(can_receive_.back());
+    can_receive_.pop_back();
+
+    auto m_opt = std::move(current_message).Take<Ms...>();
+
+    return std::move(m_opt).value();
+  }
+
+  template <Message M>
+  void Send(Address to_address, Address from_address, RequestId request_id, M &&message) {
+    std::any message_any(std::forward<M>(message));
+    OpaqueMessage opaque_message{.to_address = to_address,
+                                 .from_address = from_address,
+                                 .request_id = request_id,
+                                 .message = std::move(message_any)};
+
+    PromiseKey promise_key{
+        .requester_address = to_address, .request_id = opaque_message.request_id, .replier_address = from_address};
+
+    {
+      std::unique_lock<std::mutex> lock(mu_);
+
+      if (promises_.contains(promise_key)) {
+        spdlog::info("using message to fill promise");
+        // complete waiting promise if it's there
+        DeadlineAndOpaquePromise dop = std::move(promises_.at(promise_key));
+        promises_.erase(promise_key);
+
+        dop.promise.Fill(std::move(opaque_message));
+      } else {
+        spdlog::info("placing message in can_receive_");
+        can_receive_.emplace_back(std::move(opaque_message));
+      }
+    }  // lock dropped
+
+    cv_.notify_all();
+  }
+
+  template <Message RequestT, Message ResponseT>
+  void SubmitRequest(Address to_address, Address from_address, RequestId request_id, RequestT &&request,
+                     Duration timeout, ResponsePromise<ResponseT> promise) {
+    const bool port_matches = to_address.last_known_port == from_address.last_known_port;
+    const bool ip_matches = to_address.last_known_ip == from_address.last_known_ip;
+
+    MG_ASSERT(port_matches && ip_matches);
+    const Time deadline = Now() + timeout;
+
+    {
+      std::unique_lock<std::mutex> lock(mu_);
+
+      PromiseKey promise_key{
+          .requester_address = from_address, .request_id = request_id, .replier_address = to_address};
+      OpaquePromise opaque_promise(std::move(promise).ToUnique());
+      DeadlineAndOpaquePromise dop{.deadline = deadline, .promise = std::move(opaque_promise)};
+      promises_.emplace(std::move(promise_key), std::move(dop));
+    }  // lock dropped
+
+    Send(to_address, from_address, request_id, std::forward<RequestT>(request));
+  }
+};
+
+}  // namespace memgraph::io::local_transport

src/io/message_conversion.hpp

@@ -0,0 +1,232 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "io/transport.hpp"
+
+namespace memgraph::io {
+
+using memgraph::io::Duration;
+using memgraph::io::Message;
+using memgraph::io::Time;
+
+struct PromiseKey {
+  Address requester_address;
+  uint64_t request_id;
+  // TODO(tyler) possibly remove replier_address from promise key
+  // once we want to support DSR.
+  Address replier_address;
+
+ public:
+  friend bool operator<(const PromiseKey &lhs, const PromiseKey &rhs) {
+    if (lhs.requester_address != rhs.requester_address) {
+      return lhs.requester_address < rhs.requester_address;
+    }
+
+    if (lhs.request_id != rhs.request_id) {
+      return lhs.request_id < rhs.request_id;
+    }
+
+    return lhs.replier_address < rhs.replier_address;
+  }
+};
+
+struct OpaqueMessage {
+  Address to_address;
+  Address from_address;
+  uint64_t request_id;
+  std::any message;
+
+  /// Recursively tries to match a specific type from the outer
+  /// variant's parameter pack against the type of the std::any,
+  /// and if it matches, make it concrete and return it. Otherwise,
+  /// move on and compare the any with the next type from the
+  /// parameter pack.
+  ///
+  /// Return is the full std::variant<Ts...> type that holds the
+  /// full parameter pack without interfering with recursive
+  /// narrowing expansion.
+  template <typename Return, Message Head, Message... Rest>
+  std::optional<Return> Unpack(std::any &&a) {
+    if (typeid(Head) == a.type()) {
+      Head concrete = std::any_cast<Head>(std::move(a));
+      return concrete;
+    }
+
+    if constexpr (sizeof...(Rest) > 0) {
+      return Unpack<Return, Rest...>(std::move(a));
+    } else {
+      return std::nullopt;
+    }
+  }
+
+  /// High level "user-facing" conversion function that lets
+  /// people interested in conversion only supply a single
+  /// parameter pack for the types that they want to compare
+  /// with the any and potentially include in the returned
+  /// variant.
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) std::optional<std::variant<Ms...>> VariantFromAny(std::any &&a) {
+    return Unpack<std::variant<Ms...>, Ms...>(std::move(a));
+  }
+
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) std::optional<RequestEnvelope<Ms...>> Take() && {
+    std::optional<std::variant<Ms...>> m_opt = VariantFromAny<Ms...>(std::move(message));
+
+    if (m_opt) {
+      return RequestEnvelope<Ms...>{
+          .message = std::move(*m_opt),
+          .request_id = request_id,
+          .to_address = to_address,
+          .from_address = from_address,
+      };
+    }
+
+    return std::nullopt;
+  }
+};
+
+class OpaquePromiseTraitBase {
+ public:
+  virtual const std::type_info *TypeInfo() const = 0;
+  virtual bool IsAwaited(void *ptr) const = 0;
+  virtual void Fill(void *ptr, OpaqueMessage &&) const = 0;
+  virtual void TimeOut(void *ptr) const = 0;
+
+  virtual ~OpaquePromiseTraitBase() = default;
+  OpaquePromiseTraitBase() = default;
+  OpaquePromiseTraitBase(const OpaquePromiseTraitBase &) = delete;
+  OpaquePromiseTraitBase &operator=(const OpaquePromiseTraitBase &) = delete;
+  OpaquePromiseTraitBase(OpaquePromiseTraitBase &&old) = delete;
+  OpaquePromiseTraitBase &operator=(OpaquePromiseTraitBase &&) = delete;
+};
+
+template <typename T>
+class OpaquePromiseTrait : public OpaquePromiseTraitBase {
+ public:
+  const std::type_info *TypeInfo() const override { return &typeid(T); };
+
+  bool IsAwaited(void *ptr) const override { return static_cast<ResponsePromise<T> *>(ptr)->IsAwaited(); };
+
+  void Fill(void *ptr, OpaqueMessage &&opaque_message) const override {
+    T message = std::any_cast<T>(std::move(opaque_message.message));
+    auto response_envelope = ResponseEnvelope<T>{.message = std::move(message),
+                                                 .request_id = opaque_message.request_id,
+                                                 .to_address = opaque_message.to_address,
+                                                 .from_address = opaque_message.from_address};
+    auto promise = static_cast<ResponsePromise<T> *>(ptr);
+    auto unique_promise = std::unique_ptr<ResponsePromise<T>>(promise);
+    unique_promise->Fill(std::move(response_envelope));
+  };
+
+  void TimeOut(void *ptr) const override {
+    auto promise = static_cast<ResponsePromise<T> *>(ptr);
+    auto unique_promise = std::unique_ptr<ResponsePromise<T>>(promise);
+    ResponseResult<T> result = TimedOut{};
+    unique_promise->Fill(std::move(result));
+  }
+};
+
+class OpaquePromise {
+  void *ptr_;
+  std::unique_ptr<OpaquePromiseTraitBase> trait_;
+
+ public:
+  OpaquePromise(OpaquePromise &&old) noexcept : ptr_(old.ptr_), trait_(std::move(old.trait_)) {
+    MG_ASSERT(old.ptr_ != nullptr);
+    old.ptr_ = nullptr;
+  }
+
+  OpaquePromise &operator=(OpaquePromise &&old) noexcept {
+    MG_ASSERT(ptr_ == nullptr);
+    MG_ASSERT(old.ptr_ != nullptr);
+    MG_ASSERT(this != &old);
+    ptr_ = old.ptr_;
+    trait_ = std::move(old.trait_);
+    old.ptr_ = nullptr;
+    return *this;
+  }
+
+  OpaquePromise(const OpaquePromise &) = delete;
+  OpaquePromise &operator=(const OpaquePromise &) = delete;
+
+  template <typename T>
+  std::unique_ptr<ResponsePromise<T>> Take() && {
+    MG_ASSERT(typeid(T) == *trait_->TypeInfo());
+    MG_ASSERT(ptr_ != nullptr);
+
+    auto ptr = static_cast<ResponsePromise<T> *>(ptr_);
+
+    ptr_ = nullptr;
+
+    return std::unique_ptr<T>(ptr);
+  }
+
+  template <typename T>
+  explicit OpaquePromise(std::unique_ptr<ResponsePromise<T>> promise)
+      : ptr_(static_cast<void *>(promise.release())), trait_(std::make_unique<OpaquePromiseTrait<T>>()) {}
+
+  bool IsAwaited() {
+    MG_ASSERT(ptr_ != nullptr);
+    return trait_->IsAwaited(ptr_);
+  }
+
+  void TimeOut() {
+    MG_ASSERT(ptr_ != nullptr);
+    trait_->TimeOut(ptr_);
+    ptr_ = nullptr;
+  }
+
+  void Fill(OpaqueMessage &&opaque_message) {
+    MG_ASSERT(ptr_ != nullptr);
+    trait_->Fill(ptr_, std::move(opaque_message));
+    ptr_ = nullptr;
+  }
+
+  ~OpaquePromise() {
+    MG_ASSERT(ptr_ == nullptr, "OpaquePromise destroyed without being explicitly timed out or filled");
+  }
+};
+
+struct DeadlineAndOpaquePromise {
+  Time deadline;
+  OpaquePromise promise;
+};
+
+template <class From>
+std::type_info const &type_info_for_variant(From const &from) {
+  return std::visit([](auto &&x) -> decltype(auto) { return typeid(x); }, from);
+}
+
+template <typename From, typename Return, typename Head, typename... Rest>
+std::optional<Return> ConvertVariantInner(From &&a) {
+  if (typeid(Head) == type_info_for_variant(a)) {
+    Head concrete = std::get<Head>(std::forward<From>(a));
+    return concrete;
+  }
+
+  if constexpr (sizeof...(Rest) > 0) {
+    return ConvertVariantInner<From, Return, Rest...>(std::forward<From>(a));
+  } else {
+    return std::nullopt;
+  }
+}
+
+/// This function converts a variant to another variant holding a subset OR superset of
+/// possible types.
+template <class From, class... Ms>
+requires(sizeof...(Ms) > 0) std::optional<std::variant<Ms...>> ConvertVariant(From &&from) {
+  return ConvertVariantInner<From, std::variant<Ms...>, Ms...>(std::forward<From>(from));
+}
+
+}  // namespace memgraph::io

src/io/messages.hpp

@@ -0,0 +1,46 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <variant>
+
+#include <coordinator/coordinator.hpp>
+#include <io/rsm/raft.hpp>
+#include "query/v2/requests.hpp"
+#include "utils/concepts.hpp"
+
+namespace memgraph::io::messages {
+
+using memgraph::coordinator::CoordinatorReadRequests;
+using memgraph::coordinator::CoordinatorWriteRequests;
+using memgraph::coordinator::CoordinatorWriteResponses;
+using StorageReadRequest = msgs::ReadRequests;
+using StorageWriteRequest = msgs::WriteRequests;
+
+using memgraph::io::rsm::AppendRequest;
+using memgraph::io::rsm::AppendResponse;
+using memgraph::io::rsm::ReadRequest;
+using memgraph::io::rsm::VoteRequest;
+using memgraph::io::rsm::VoteResponse;
+using memgraph::io::rsm::WriteRequest;
+using memgraph::io::rsm::WriteResponse;
+
+using CoordinatorMessages =
+    std::variant<ReadRequest<CoordinatorReadRequests>, AppendRequest<CoordinatorWriteRequests>, AppendResponse,
+                 WriteRequest<CoordinatorWriteRequests>, VoteRequest, VoteResponse>;
+
+using ShardMessages = std::variant<ReadRequest<StorageReadRequest>, AppendRequest<StorageWriteRequest>, AppendResponse,
+                                   WriteRequest<StorageWriteRequest>, VoteRequest, VoteResponse>;
+
+using ShardManagerMessages = std::variant<WriteResponse<CoordinatorWriteResponses>>;
+
+}  // namespace memgraph::io::messages

src/io/rsm/raft.hpp

@@ -0,0 +1,926 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+// TODO(tyler) buffer out-of-order Append buffers on the Followers to reassemble more quickly
+// TODO(tyler) handle granular batch sizes based on simple flow control
+
+#pragma once
+
+#include <deque>
+#include <iostream>
+#include <map>
+#include <set>
+#include <thread>
+#include <unordered_map>
+#include <vector>
+
+#include "io/simulator/simulator.hpp"
+#include "io/transport.hpp"
+#include "utils/concepts.hpp"
+
+namespace memgraph::io::rsm {
+
+/// Timeout and replication tunables
+using namespace std::chrono_literals;
+static constexpr auto kMinimumElectionTimeout = 100ms;
+static constexpr auto kMaximumElectionTimeout = 200ms;
+static constexpr auto kMinimumBroadcastTimeout = 40ms;
+static constexpr auto kMaximumBroadcastTimeout = 60ms;
+static constexpr auto kMinimumCronInterval = 1ms;
+static constexpr auto kMaximumCronInterval = 2ms;
+static constexpr auto kMinimumReceiveTimeout = 40ms;
+static constexpr auto kMaximumReceiveTimeout = 60ms;
+static_assert(kMinimumElectionTimeout > kMaximumBroadcastTimeout,
+              "The broadcast timeout has to be smaller than the election timeout!");
+static_assert(kMinimumElectionTimeout < kMaximumElectionTimeout,
+              "The minimum election timeout has to be smaller than the maximum election timeout!");
+static_assert(kMinimumBroadcastTimeout < kMaximumBroadcastTimeout,
+              "The minimum broadcast timeout has to be smaller than the maximum broadcast timeout!");
+static_assert(kMinimumCronInterval < kMaximumCronInterval,
+              "The minimum cron interval has to be smaller than the maximum cron interval!");
+static_assert(kMinimumReceiveTimeout < kMaximumReceiveTimeout,
+              "The minimum receive timeout has to be smaller than the maximum receive timeout!");
+static constexpr size_t kMaximumAppendBatchSize = 1024;
+
+using Term = uint64_t;
+using LogIndex = uint64_t;
+using LogSize = uint64_t;
+
+template <typename WriteOperation>
+struct WriteRequest {
+  WriteOperation operation;
+};
+
+/// WriteResponse is returned to a client after
+/// their WriteRequest was entered in to the raft
+/// log and it reached consensus.
+///
+/// WriteReturn is the result of applying the WriteRequest to
+/// ReplicatedState, and if the ReplicatedState::write
+/// method is deterministic, all replicas will
+/// have the same ReplicatedState after applying
+/// the submitted WriteRequest.
+template <typename WriteReturn>
+struct WriteResponse {
+  bool success;
+  WriteReturn write_return;
+  std::optional<Address> retry_leader;
+  LogIndex raft_index;
+};
+
+template <typename ReadOperation>
+struct ReadRequest {
+  ReadOperation operation;
+};
+
+template <typename ReadReturn>
+struct ReadResponse {
+  bool success;
+  ReadReturn read_return;
+  std::optional<Address> retry_leader;
+};
+
+/// AppendRequest is a raft-level message that the Leader
+/// periodically broadcasts to all Follower peers. This
+/// serves three main roles:
+/// 1. acts as a heartbeat from the Leader to the Follower
+/// 2. replicates new data that the Leader has received to the Follower
+/// 3. informs Follower peers when the commit index has increased,
+///    signalling that it is now safe to apply log items to the
+///    replicated state machine
+template <typename WriteRequest>
+struct AppendRequest {
+  Term term = 0;
+  LogIndex batch_start_log_index;
+  Term last_log_term;
+  std::vector<std::pair<Term, WriteRequest>> entries;
+  LogSize leader_commit;
+};
+
+struct AppendResponse {
+  bool success;
+  Term term;
+  Term last_log_term;
+  // a small optimization over the raft paper, tells
+  // the leader the offset that we are interested in
+  // to send log offsets from for us. This will only
+  // be useful at the beginning of a leader's term.
+  LogSize log_size;
+};
+
+struct VoteRequest {
+  Term term = 0;
+  LogSize log_size;
+  Term last_log_term;
+};
+
+struct VoteResponse {
+  Term term = 0;
+  LogSize committed_log_size;
+  bool vote_granted = false;
+};
+
+template <typename WriteRequest>
+struct CommonState {
+  Term term = 0;
+  std::vector<std::pair<Term, WriteRequest>> log;
+  LogSize committed_log_size = 0;
+  LogSize applied_size = 0;
+};
+
+struct FollowerTracker {
+  LogIndex next_index = 0;
+  LogSize confirmed_log_size = 0;
+};
+
+struct PendingClientRequest {
+  RequestId request_id;
+  Address address;
+  Time received_at;
+};
+
+struct Leader {
+  std::map<Address, FollowerTracker> followers;
+  std::unordered_map<LogIndex, PendingClientRequest> pending_client_requests;
+  Time last_broadcast = Time::min();
+
+  std::string static ToString() { return "\tLeader   \t"; }
+};
+
+struct Candidate {
+  std::map<Address, LogSize> successful_votes;
+  Time election_began = Time::min();
+  std::set<Address> outstanding_votes;
+
+  std::string static ToString() { return "\tCandidate\t"; }
+};
+
+struct Follower {
+  Time last_received_append_entries_timestamp;
+  Address leader_address;
+
+  std::string static ToString() { return "\tFollower \t"; }
+};
+
+using Role = std::variant<Candidate, Leader, Follower>;
+
+template <typename Role>
+concept AllRoles = memgraph::utils::SameAsAnyOf<Role, Leader, Follower, Candidate>;
+
+template <typename Role>
+concept LeaderOrFollower = memgraph::utils::SameAsAnyOf<Role, Leader, Follower>;
+
+template <typename Role>
+concept FollowerOrCandidate = memgraph::utils::SameAsAnyOf<Role, Follower, Candidate>;
+
+/*
+all ReplicatedState classes should have an Apply method
+that returns our WriteResponseValue after consensus, and
+a Read method that returns our ReadResponseValue without
+requiring consensus.
+
+ReadResponse Read(ReadOperation);
+WriteResponseValue ReplicatedState::Apply(WriteRequest);
+
+For example:
+If the state is uint64_t, and WriteRequest is `struct PlusOne {};`,
+and WriteResponseValue is also uint64_t (the new value), then
+each call to state.Apply(PlusOne{}) will return the new value
+after incrementing it. 0, 1, 2, 3... and this will be sent back
+to the client that requested the mutation.
+
+In practice, these mutations will usually be predicated on some
+previous value, so that they are idempotent, functioning similarly
+to a CAS operation.
+*/
+template <typename WriteOperation, typename ReadOperation, typename ReplicatedState, typename WriteResponseValue,
+          typename ReadResponseValue>
+concept Rsm = requires(ReplicatedState state, WriteOperation w, ReadOperation r) {
+  { state.Read(r) } -> std::same_as<ReadResponseValue>;
+  { state.Apply(w) } -> std::same_as<WriteResponseValue>;
+};
+
+/// Parameter           Purpose
+/// --------------------------
+/// IoImpl              the concrete Io provider - SimulatorTransport, ThriftTransport, etc...
+/// ReplicatedState     the high-level data structure that is managed by the raft-backed replicated state machine
+/// WriteOperation      the individual operation type that is applied to the ReplicatedState in identical order
+///                     across each replica
+/// WriteResponseValue  the return value of calling ReplicatedState::Apply(WriteOperation), which is executed in
+///                     identical order across all replicas after an WriteOperation reaches consensus.
+/// ReadOperation       the type of operations that do not require consensus before executing directly
+///                     on a const ReplicatedState &
+/// ReadResponseValue   the return value of calling ReplicatedState::Read(ReadOperation), which is executed directly
+///                     without going through consensus first
+template <typename IoImpl, typename ReplicatedState, typename WriteOperation, typename WriteResponseValue,
+          typename ReadOperation, typename ReadResponseValue>
+requires Rsm<WriteOperation, ReadOperation, ReplicatedState, WriteResponseValue, ReadResponseValue>
+class Raft {
+  CommonState<WriteOperation> state_;
+  Role role_ = Candidate{};
+  Io<IoImpl> io_;
+  std::vector<Address> peers_;
+  ReplicatedState replicated_state_;
+  Time next_cron_;
+
+ public:
+  Raft(Io<IoImpl> &&io, std::vector<Address> peers, ReplicatedState &&replicated_state)
+      : io_(std::forward<Io<IoImpl>>(io)),
+        peers_(peers),
+        replicated_state_(std::forward<ReplicatedState>(replicated_state)) {
+    if (peers.empty()) {
+      role_ = Leader{};
+    }
+  }
+
+  /// Periodic protocol maintenance. Returns the time that Cron should be called again
+  /// in the future.
+  Time Cron() {
+    // dispatch periodic logic based on our role to a specific Cron method.
+    std::optional<Role> new_role = std::visit([&](auto &role) { return Cron(role); }, role_);
+
+    if (new_role) {
+      role_ = std::move(new_role).value();
+    }
+    const Duration random_cron_interval = RandomTimeout(kMinimumCronInterval, kMaximumCronInterval);
+
+    return io_.Now() + random_cron_interval;
+  }
+
+  /// Returns the Address for our underlying Io implementation
+  Address GetAddress() { return io_.GetAddress(); }
+
+  using ReceiveVariant = std::variant<ReadRequest<ReadOperation>, AppendRequest<WriteOperation>, AppendResponse,
+                                      WriteRequest<WriteOperation>, VoteRequest, VoteResponse>;
+
+  void Handle(ReceiveVariant &&message_variant, RequestId request_id, Address from_address) {
+    // dispatch the message to a handler based on our role,
+    // which can be specified in the Handle first argument,
+    // or it can be `auto` if it's a handler for several roles
+    // or messages.
+    std::optional<Role> new_role = std::visit(
+        [&](auto &&msg, auto &role) mutable {
+          return Handle(role, std::forward<decltype(msg)>(msg), request_id, from_address);
+        },
+        std::forward<ReceiveVariant>(message_variant), role_);
+
+    // TODO(tyler) (M3) maybe replace std::visit with get_if for explicit prioritized matching, [[likely]] etc...
+    if (new_role) {
+      role_ = std::move(new_role).value();
+    }
+  }
+
+  void Run() {
+    while (!io_.ShouldShutDown()) {
+      const auto now = io_.Now();
+      if (now >= next_cron_) {
+        next_cron_ = Cron();
+      }
+
+      const Duration receive_timeout = RandomTimeout(kMinimumReceiveTimeout, kMaximumReceiveTimeout);
+
+      auto request_result =
+          io_.template ReceiveWithTimeout<ReadRequest<ReadOperation>, AppendRequest<WriteOperation>, AppendResponse,
+                                          WriteRequest<WriteOperation>, VoteRequest, VoteResponse>(receive_timeout);
+      if (request_result.HasError()) {
+        continue;
+      }
+
+      auto request = std::move(request_result.GetValue());
+
+      Handle(std::move(request.message), request.request_id, request.from_address);
+    }
+  }
+
+ private:
+  // Raft paper - 5.3
+  // When the entry has been safely replicated, the leader applies the
+  // entry to its state machine and returns the result of that
+  // execution to the client.
+  //
+  // "Safely replicated" is defined as being known to be present
+  // on at least a majority of all peers (inclusive of the Leader).
+  void BumpCommitIndexAndReplyToClients(Leader &leader) {
+    auto confirmed_log_sizes = std::vector<LogSize>{};
+
+    // We include our own log size in the calculation of the log
+    // confirmed log size that is present on at least a majority of all peers.
+    confirmed_log_sizes.push_back(state_.log.size());
+
+    for (const auto &[addr, f] : leader.followers) {
+      confirmed_log_sizes.push_back(f.confirmed_log_size);
+      Log("Follower at port ", addr.last_known_port, " has confirmed log size of: ", f.confirmed_log_size);
+    }
+
+    // reverse sort from highest to lowest (using std::ranges::greater)
+    std::ranges::sort(confirmed_log_sizes, std::ranges::greater());
+
+    // This is a particularly correctness-critical calculation because it
+    // determines the committed log size that will be broadcast in
+    // the next AppendRequest.
+    //
+    // If the following sizes are recorded for clusters of different numbers of peers,
+    // these are the expected sizes that are considered to have reached consensus:
+    //
+    // state           | expected value | (confirmed_log_sizes.size() / 2)
+    // [1]              1                 (1 / 2) => 0
+    // [2, 1]           1                 (2 / 2) => 1
+    // [3, 2, 1]        2                 (3 / 2) => 1
+    // [4, 3, 2, 1]     2                 (4 / 2) => 2
+    // [5, 4, 3, 2, 1]  3                 (5 / 2) => 2
+    const size_t majority_index = confirmed_log_sizes.size() / 2;
+    const LogSize new_committed_log_size = confirmed_log_sizes[majority_index];
+
+    // We never go backwards in history.
+    MG_ASSERT(state_.committed_log_size <= new_committed_log_size,
+              "as a Leader, we have previously set our committed_log_size to {}, but our Followers have a majority "
+              "committed_log_size of {}",
+              state_.committed_log_size, new_committed_log_size);
+
+    state_.committed_log_size = new_committed_log_size;
+
+    // For each size between the old size and the new one (inclusive),
+    // Apply that log's WriteOperation to our replicated_state_,
+    // and use the specific return value of the ReplicatedState::Apply
+    // method (WriteResponseValue) to respond to the requester.
+    for (; state_.applied_size < state_.committed_log_size; state_.applied_size++) {
+      const LogIndex apply_index = state_.applied_size;
+      const auto &write_request = state_.log[apply_index].second;
+      const WriteResponseValue write_return = replicated_state_.Apply(write_request);
+
+      if (leader.pending_client_requests.contains(apply_index)) {
+        const PendingClientRequest client_request = std::move(leader.pending_client_requests.at(apply_index));
+        leader.pending_client_requests.erase(apply_index);
+
+        const WriteResponse<WriteResponseValue> resp{
+            .success = true,
+            .write_return = std::move(write_return),
+            .raft_index = apply_index,
+        };
+
+        io_.Send(client_request.address, client_request.request_id, std::move(resp));
+      }
+    }
+
+    Log("committed_log_size is now ", state_.committed_log_size);
+  }
+
+  // Raft paper - 5.1
+  // AppendEntries RPCs are initiated by leaders to replicate log entries and to provide a form of heartbeat
+  void BroadcastAppendEntries(std::map<Address, FollowerTracker> &followers) {
+    for (auto &[address, follower] : followers) {
+      const LogIndex next_index = follower.next_index;
+
+      const auto missing = state_.log.size() - next_index;
+      const auto batch_size = std::min(missing, kMaximumAppendBatchSize);
+      const auto start_index = next_index;
+      const auto end_index = start_index + batch_size;
+
+      // advance follower's next index
+      follower.next_index += batch_size;
+
+      std::vector<std::pair<Term, WriteOperation>> entries;
+
+      entries.insert(entries.begin(), state_.log.begin() + start_index, state_.log.begin() + end_index);
+
+      const Term previous_term_from_index = PreviousTermFromIndex(start_index);
+
+      Log("sending ", entries.size(), " entries to Follower ", address.last_known_port,
+          " which are above its next_index of ", next_index);
+
+      AppendRequest<WriteOperation> ar{
+          .term = state_.term,
+          .batch_start_log_index = start_index,
+          .last_log_term = previous_term_from_index,
+          .entries = std::move(entries),
+          .leader_commit = state_.committed_log_size,
+      };
+
+      // request_id not necessary to set because it's not a Future-backed Request.
+      static constexpr RequestId request_id = 0;
+
+      io_.Send(address, request_id, std::move(ar));
+    }
+  }
+
+  // Raft paper - 5.2
+  // Raft uses randomized election timeouts to ensure that split votes are rare and that they are resolved quickly
+  Duration RandomTimeout(Duration min, Duration max) {
+    std::uniform_int_distribution time_distrib(min.count(), max.count());
+
+    const auto rand_micros = io_.Rand(time_distrib);
+
+    return Duration{rand_micros};
+  }
+
+  Duration RandomTimeout(int min_micros, int max_micros) {
+    std::uniform_int_distribution time_distrib(min_micros, max_micros);
+
+    const int rand_micros = io_.Rand(time_distrib);
+
+    return std::chrono::microseconds{rand_micros};
+  }
+
+  Term PreviousTermFromIndex(LogIndex index) const {
+    if (index == 0 || state_.log.size() + 1 <= index) {
+      return 0;
+    }
+
+    const auto &[term, data] = state_.log.at(index - 1);
+    return term;
+  }
+
+  Term CommittedLogTerm() {
+    MG_ASSERT(state_.log.size() >= state_.committed_log_size);
+    if (state_.log.empty() || state_.committed_log_size == 0) {
+      return 0;
+    }
+
+    const auto &[term, data] = state_.log.at(state_.committed_log_size - 1);
+    return term;
+  }
+
+  Term LastLogTerm() const {
+    if (state_.log.empty()) {
+      return 0;
+    }
+
+    const auto &[term, data] = state_.log.back();
+    return term;
+  }
+
+  template <typename... Ts>
+  void Log(Ts &&...args) {
+    const Time now = io_.Now();
+    const auto micros = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count();
+    const Term term = state_.term;
+    const std::string role_string = std::visit([&](const auto &role) { return role.ToString(); }, role_);
+
+    std::ostringstream out;
+
+    out << '\t' << static_cast<int>(micros) << "\t" << term << "\t" << io_.GetAddress().last_known_port;
+
+    out << role_string;
+
+    (out << ... << args);
+
+    spdlog::info(out.str());
+  }
+
+  /////////////////////////////////////////////////////////////
+  /// Raft-related Cron methods
+  ///
+  /// Cron + std::visit is how events are dispatched
+  /// to certain code based on Raft role.
+  ///
+  /// Cron(role) takes as the first argument a reference to its
+  /// role, and as the second argument, the message that has
+  /// been received.
+  /////////////////////////////////////////////////////////////
+
+  // Raft paper - 5.2
+  // Candidates keep sending Vote to peers until:
+  // 1. receiving Append with a higher term (become Follower)
+  // 2. receiving Vote with a higher term (become a Follower)
+  // 3. receiving a quorum of responses to our last batch of Vote (become a Leader)
+  std::optional<Role> Cron(Candidate &candidate) {
+    const auto now = io_.Now();
+    const Duration election_timeout = RandomTimeout(kMinimumElectionTimeout, kMaximumElectionTimeout);
+    const auto election_timeout_us = std::chrono::duration_cast<std::chrono::milliseconds>(election_timeout).count();
+
+    if (now - candidate.election_began > election_timeout) {
+      state_.term++;
+      Log("becoming Candidate for term ", state_.term, " after leader timeout of ", election_timeout_us,
+          "ms elapsed since last election attempt");
+
+      const VoteRequest request{
+          .term = state_.term,
+          .log_size = state_.log.size(),
+          .last_log_term = LastLogTerm(),
+      };
+
+      auto outstanding_votes = std::set<Address>();
+
+      for (const auto &peer : peers_) {
+        // request_id not necessary to set because it's not a Future-backed Request.
+        static constexpr auto request_id = 0;
+        io_.template Send<VoteRequest>(peer, request_id, request);
+        outstanding_votes.insert(peer);
+      }
+
+      return Candidate{
+          .successful_votes = std::map<Address, LogIndex>(),
+          .election_began = now,
+          .outstanding_votes = outstanding_votes,
+      };
+    }
+    return std::nullopt;
+  }
+
+  // Raft paper - 5.2
+  // Followers become candidates if we haven't heard from the leader
+  // after a randomized timeout.
+  std::optional<Role> Cron(Follower &follower) {
+    const auto now = io_.Now();
+    const auto time_since_last_append_entries = now - follower.last_received_append_entries_timestamp;
+
+    // randomized follower timeout
+    const Duration election_timeout = RandomTimeout(kMinimumElectionTimeout, kMaximumElectionTimeout);
+
+    if (time_since_last_append_entries > election_timeout) {
+      // become a Candidate if we haven't heard from the Leader after this timeout
+      return Candidate{};
+    }
+
+    return std::nullopt;
+  }
+
+  // Leaders (re)send AppendRequest to followers.
+  std::optional<Role> Cron(Leader &leader) {
+    const Time now = io_.Now();
+    const Duration broadcast_timeout = RandomTimeout(kMinimumBroadcastTimeout, kMaximumBroadcastTimeout);
+
+    if (now - leader.last_broadcast > broadcast_timeout) {
+      BroadcastAppendEntries(leader.followers);
+      leader.last_broadcast = now;
+    }
+
+    return std::nullopt;
+  }
+
+  /////////////////////////////////////////////////////////////
+  /// Raft-related Handle methods
+  ///
+  /// Handle + std::visit is how events are dispatched
+  /// to certain code based on Raft role.
+  ///
+  /// Handle(role, message, ...)
+  /// takes as the first argument a reference
+  /// to its role, and as the second argument, the
+  /// message that has been received.
+  /////////////////////////////////////////////////////////////
+
+  // all roles can receive Vote and possibly become a follower
+  template <AllRoles ALL>
+  std::optional<Role> Handle(ALL & /* variable */, VoteRequest &&req, RequestId request_id, Address from_address) {
+    Log("received VoteRequest from ", from_address.last_known_port, " with term ", req.term);
+    const bool last_log_term_dominates = req.last_log_term >= LastLogTerm();
+    const bool term_dominates = req.term > state_.term;
+    const bool log_size_dominates = req.log_size >= state_.log.size();
+    const bool new_leader = last_log_term_dominates && term_dominates && log_size_dominates;
+
+    if (new_leader) {
+      MG_ASSERT(req.term > state_.term);
+      MG_ASSERT(std::max(req.term, state_.term) == req.term);
+    }
+
+    const VoteResponse res{
+        .term = std::max(req.term, state_.term),
+        .committed_log_size = state_.committed_log_size,
+        .vote_granted = new_leader,
+    };
+
+    io_.Send(from_address, request_id, res);
+
+    if (new_leader) {
+      // become a follower
+      state_.term = req.term;
+      return Follower{
+          .last_received_append_entries_timestamp = io_.Now(),
+          .leader_address = from_address,
+      };
+    }
+
+    if (term_dominates) {
+      Log("received a vote from an inferior candidate. Becoming Candidate");
+      state_.term = std::max(state_.term, req.term) + 1;
+      return Candidate{};
+    }
+
+    return std::nullopt;
+  }
+
+  std::optional<Role> Handle(Candidate &candidate, VoteResponse &&res, RequestId /* variable */, Address from_address) {
+    Log("received VoteResponse");
+
+    if (!res.vote_granted || res.term != state_.term) {
+      Log("received unsuccessful VoteResponse from term ", res.term, " when our candidacy term is ", state_.term);
+      // we received a delayed VoteResponse from the past, which has to do with an election that is
+      // no longer valid. We can simply drop this.
+      return std::nullopt;
+    }
+
+    MG_ASSERT(candidate.outstanding_votes.contains(from_address),
+              "Received unexpected VoteResponse from server not present in Candidate's outstanding_votes!");
+    candidate.outstanding_votes.erase(from_address);
+
+    MG_ASSERT(!candidate.successful_votes.contains(from_address),
+              "Received unexpected VoteResponse from server already in Candidate's successful_votes!");
+    candidate.successful_votes.insert({from_address, res.committed_log_size});
+
+    if (candidate.successful_votes.size() >= candidate.outstanding_votes.size()) {
+      std::map<Address, FollowerTracker> followers{};
+
+      for (const auto &[address, committed_log_size] : candidate.successful_votes) {
+        FollowerTracker follower{
+            .next_index = committed_log_size,
+            .confirmed_log_size = committed_log_size,
+        };
+        followers.insert({address, follower});
+      }
+      for (const auto &address : candidate.outstanding_votes) {
+        FollowerTracker follower{
+            .next_index = state_.log.size(),
+            .confirmed_log_size = 0,
+        };
+        followers.insert({address, follower});
+      }
+
+      Log("becoming Leader at term ", state_.term);
+
+      BroadcastAppendEntries(followers);
+
+      return Leader{
+          .followers = std::move(followers),
+          .pending_client_requests = std::unordered_map<LogIndex, PendingClientRequest>(),
+      };
+    }
+
+    return std::nullopt;
+  }
+
+  template <LeaderOrFollower LOF>
+  std::optional<Role> Handle(LOF & /* variable */, VoteResponse && /* variable */, RequestId /* variable */,
+                             Address /* variable */) {
+    Log("non-Candidate received VoteResponse");
+    return std::nullopt;
+  }
+
+  template <AllRoles ALL>
+  std::optional<Role> Handle(ALL &role, AppendRequest<WriteOperation> &&req, RequestId request_id,
+                             Address from_address) {
+    // log size starts out as state_.committed_log_size and only if everything is successful do we
+    // switch it to the log length.
+    AppendResponse res{
+        .success = false,
+        .term = state_.term,
+        .last_log_term = CommittedLogTerm(),
+        .log_size = state_.log.size(),
+    };
+
+    if constexpr (std::is_same<ALL, Leader>()) {
+      MG_ASSERT(req.term != state_.term, "Multiple leaders are acting under the term ", req.term);
+    }
+
+    const bool is_candidate = std::is_same<ALL, Candidate>();
+    const bool is_failed_competitor = is_candidate && req.term == state_.term;
+    const Time now = io_.Now();
+
+    // Raft paper - 5.2
+    // While waiting for votes, a candidate may receive an
+    // AppendEntries RPC from another server claiming to be leader. If
+    // the leader’s term (included in its RPC) is at least as large as
+    // the candidate’s current term, then the candidate recognizes the
+    // leader as legitimate and returns to follower state.
+    if (req.term > state_.term || is_failed_competitor) {
+      // become follower of this leader, reply with our log status
+      state_.term = req.term;
+
+      io_.Send(from_address, request_id, res);
+
+      Log("becoming Follower of Leader ", from_address.last_known_port, " at term ", req.term);
+      return Follower{
+          .last_received_append_entries_timestamp = now,
+          .leader_address = from_address,
+      };
+    }
+
+    if (req.term < state_.term) {
+      // nack this request from an old leader
+      io_.Send(from_address, request_id, res);
+
+      return std::nullopt;
+    }
+
+    // at this point, we're dealing with our own leader
+    if constexpr (std::is_same<ALL, Follower>()) {
+      // small specialization for when we're already a Follower
+      MG_ASSERT(role.leader_address == from_address, "Multiple Leaders are acting under the same term number!");
+      role.last_received_append_entries_timestamp = now;
+    } else {
+      Log("Somehow entered Follower-specific logic as a non-Follower");
+      MG_ASSERT(false, "Somehow entered Follower-specific logic as a non-Follower");
+    }
+
+    // Handle steady-state conditions.
+    if (req.batch_start_log_index != state_.log.size()) {
+      Log("req.batch_start_log_index of ", req.batch_start_log_index, " does not match our log size of ",
+          state_.log.size());
+    } else if (req.last_log_term != LastLogTerm()) {
+      Log("req.last_log_term differs from our leader term at that slot, expected: ", LastLogTerm(), " but got ",
+          req.last_log_term);
+    } else {
+      // happy path - Apply log
+      Log("applying batch of ", req.entries.size(), " entries to our log starting at index ",
+          req.batch_start_log_index);
+
+      const auto resize_length = req.batch_start_log_index;
+
+      MG_ASSERT(resize_length >= state_.committed_log_size,
+                "Applied history from Leader which goes back in time from our commit_index");
+
+      // possibly chop-off stuff that was replaced by
+      // things with different terms (we got data that
+      // hasn't reached consensus yet, which is normal)
+      state_.log.resize(resize_length);
+
+      if (req.entries.size() > 0) {
+        auto &[first_term, op] = req.entries.at(0);
+        MG_ASSERT(LastLogTerm() <= first_term);
+      }
+
+      state_.log.insert(state_.log.end(), std::make_move_iterator(req.entries.begin()),
+                        std::make_move_iterator(req.entries.end()));
+
+      MG_ASSERT(req.leader_commit >= state_.committed_log_size);
+      state_.committed_log_size = std::min(req.leader_commit, state_.log.size());
+
+      for (; state_.applied_size < state_.committed_log_size; state_.applied_size++) {
+        const auto &write_request = state_.log[state_.applied_size].second;
+        replicated_state_.Apply(write_request);
+      }
+
+      res.success = true;
+    }
+
+    res.last_log_term = LastLogTerm();
+    res.log_size = state_.log.size();
+
+    Log("returning log_size of ", res.log_size);
+
+    io_.Send(from_address, request_id, res);
+
+    return std::nullopt;
+  }
+
+  std::optional<Role> Handle(Leader &leader, AppendResponse &&res, RequestId /* variable */, Address from_address) {
+    if (res.term != state_.term) {
+      Log("received AppendResponse related to a previous term when we (presumably) were the leader");
+      return std::nullopt;
+    }
+
+    // TODO(tyler) when we have dynamic membership, this assert will become incorrect, but we should
+    // keep it in-place until then because it has bug finding value.
+    MG_ASSERT(leader.followers.contains(from_address), "received AppendResponse from unknown Follower");
+
+    // at this point, we know the term matches and we know this Follower
+
+    FollowerTracker &follower = leader.followers.at(from_address);
+
+    if (res.success) {
+      Log("got successful AppendResponse from ", from_address.last_known_port, " with log_size of ", res.log_size);
+      follower.next_index = std::max(follower.next_index, res.log_size);
+    } else {
+      Log("got unsuccessful AppendResponse from ", from_address.last_known_port, " with log_size of ", res.log_size);
+      follower.next_index = res.log_size;
+    }
+
+    follower.confirmed_log_size = std::max(follower.confirmed_log_size, res.log_size);
+
+    BumpCommitIndexAndReplyToClients(leader);
+
+    return std::nullopt;
+  }
+
+  template <FollowerOrCandidate FOC>
+  std::optional<Role> Handle(FOC & /* variable */, AppendResponse && /* variable */, RequestId /* variable */,
+                             Address /* variable */) {
+    // we used to be the leader, and are getting old delayed responses
+    return std::nullopt;
+  }
+
+  /////////////////////////////////////////////////////////////
+  /// RSM-related handle methods
+  /////////////////////////////////////////////////////////////
+
+  // Leaders are able to immediately respond to the requester (with a ReadResponseValue) applied to the ReplicatedState
+  std::optional<Role> Handle(Leader & /* variable */, ReadRequest<ReadOperation> &&req, RequestId request_id,
+                             Address from_address) {
+    Log("handling ReadOperation");
+    ReadOperation read_operation = req.operation;
+
+    ReadResponseValue read_return = replicated_state_.Read(read_operation);
+
+    const ReadResponse<ReadResponseValue> resp{
+        .success = true,
+        .read_return = std::move(read_return),
+        .retry_leader = std::nullopt,
+    };
+
+    io_.Send(from_address, request_id, resp);
+
+    return std::nullopt;
+  }
+
+  // Candidates should respond with a failure, similar to the Candidate + WriteRequest failure below
+  std::optional<Role> Handle(Candidate & /* variable */, ReadRequest<ReadOperation> && /* variable */,
+                             RequestId request_id, Address from_address) {
+    Log("received ReadOperation - not redirecting because no Leader is known");
+    const ReadResponse<ReadResponseValue> res{
+        .success = false,
+    };
+
+    io_.Send(from_address, request_id, res);
+
+    Cron();
+
+    return std::nullopt;
+  }
+
+  // Followers should respond with a redirection, similar to the Follower + WriteRequest response below
+  std::optional<Role> Handle(Follower &follower, ReadRequest<ReadOperation> && /* variable */, RequestId request_id,
+                             Address from_address) {
+    Log("redirecting client to known Leader with port ", follower.leader_address.last_known_port);
+
+    const ReadResponse<ReadResponseValue> res{
+        .success = false,
+        .retry_leader = follower.leader_address,
+    };
+
+    io_.Send(from_address, request_id, res);
+
+    return std::nullopt;
+  }
+
+  // Raft paper - 8
+  // When a client first starts up, it connects to a randomly chosen
+  // server. If the client’s first choice is not the leader, that
+  // server will reject the client’s request and supply information
+  // about the most recent leader it has heard from.
+  std::optional<Role> Handle(Follower &follower, WriteRequest<WriteOperation> && /* variable */, RequestId request_id,
+                             Address from_address) {
+    Log("redirecting client to known Leader with port ", follower.leader_address.last_known_port);
+
+    const WriteResponse<WriteResponseValue> res{
+        .success = false,
+        .retry_leader = follower.leader_address,
+    };
+
+    io_.Send(from_address, request_id, res);
+
+    return std::nullopt;
+  }
+
+  std::optional<Role> Handle(Candidate & /* variable */, WriteRequest<WriteOperation> && /* variable */,
+                             RequestId request_id, Address from_address) {
+    Log("received WriteRequest - not redirecting because no Leader is known");
+
+    const WriteResponse<WriteResponseValue> res{
+        .success = false,
+    };
+
+    io_.Send(from_address, request_id, res);
+
+    Cron();
+
+    return std::nullopt;
+  }
+
+  // only leaders actually handle replication requests from clients
+  std::optional<Role> Handle(Leader &leader, WriteRequest<WriteOperation> &&req, RequestId request_id,
+                             Address from_address) {
+    Log("handling WriteRequest");
+
+    // we are the leader. add item to log and send Append to peers
+    MG_ASSERT(state_.term >= LastLogTerm());
+    state_.log.emplace_back(std::pair(state_.term, std::move(req.operation)));
+
+    LogIndex log_index = state_.log.size() - 1;
+
+    PendingClientRequest pcr{
+        .request_id = request_id,
+        .address = from_address,
+        .received_at = io_.Now(),
+    };
+
+    leader.pending_client_requests.emplace(log_index, pcr);
+
+    if (peers_.empty()) {
+      BumpCommitIndexAndReplyToClients(leader);
+    } else {
+      BroadcastAppendEntries(leader.followers);
+    }
+
+    return std::nullopt;
+  }
+};
+
+};  // namespace memgraph::io::rsm

src/io/rsm/rsm_client.hpp

@@ -0,0 +1,136 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <iostream>
+#include <optional>
+#include <vector>
+
+#include "io/address.hpp"
+#include "io/rsm/raft.hpp"
+#include "utils/result.hpp"
+
+namespace memgraph::io::rsm {
+
+using memgraph::io::Address;
+using memgraph::io::Duration;
+using memgraph::io::ResponseEnvelope;
+using memgraph::io::ResponseFuture;
+using memgraph::io::ResponseResult;
+using memgraph::io::Time;
+using memgraph::io::TimedOut;
+using memgraph::io::rsm::ReadRequest;
+using memgraph::io::rsm::ReadResponse;
+using memgraph::io::rsm::WriteRequest;
+using memgraph::io::rsm::WriteResponse;
+using memgraph::utils::BasicResult;
+
+template <typename IoImpl, typename WriteRequestT, typename WriteResponseT, typename ReadRequestT,
+          typename ReadResponseT>
+class RsmClient {
+  using ServerPool = std::vector<Address>;
+
+  Io<IoImpl> io_;
+  Address leader_;
+  ServerPool server_addrs_;
+
+  template <typename ResponseT>
+  void PossiblyRedirectLeader(const ResponseT &response) {
+    if (response.retry_leader) {
+      MG_ASSERT(!response.success, "retry_leader should never be set for successful responses");
+      leader_ = response.retry_leader.value();
+      spdlog::debug("client redirected to leader server {}", leader_.ToString());
+    } else if (!response.success) {
+      std::uniform_int_distribution<size_t> addr_distrib(0, (server_addrs_.size() - 1));
+      size_t addr_index = io_.Rand(addr_distrib);
+      leader_ = server_addrs_[addr_index];
+
+      spdlog::debug(
+          "client NOT redirected to leader server despite our success failing to be processed (it probably was sent to "
+          "a RSM Candidate) trying a random one at index {} with address {}",
+          addr_index, leader_.ToString());
+    }
+  }
+
+ public:
+  RsmClient(Io<IoImpl> io, Address leader, ServerPool server_addrs)
+      : io_{io}, leader_{leader}, server_addrs_{server_addrs} {}
+
+  RsmClient() = delete;
+
+  BasicResult<TimedOut, WriteResponseT> SendWriteRequest(WriteRequestT req) {
+    WriteRequest<WriteRequestT> client_req;
+    client_req.operation = req;
+
+    const Duration overall_timeout = io_.GetDefaultTimeout();
+    const Time before = io_.Now();
+
+    do {
+      spdlog::debug("client sending WriteRequest to Leader {}", leader_.ToString());
+      ResponseFuture<WriteResponse<WriteResponseT>> response_future =
+          io_.template Request<WriteRequest<WriteRequestT>, WriteResponse<WriteResponseT>>(leader_, client_req);
+      ResponseResult<WriteResponse<WriteResponseT>> response_result = std::move(response_future).Wait();
+
+      if (response_result.HasError()) {
+        spdlog::debug("client timed out while trying to communicate with leader server {}", leader_.ToString());
+        return response_result.GetError();
+      }
+
+      ResponseEnvelope<WriteResponse<WriteResponseT>> &&response_envelope = std::move(response_result.GetValue());
+      WriteResponse<WriteResponseT> &&write_response = std::move(response_envelope.message);
+
+      if (write_response.success) {
+        return std::move(write_response.write_return);
+      }
+
+      PossiblyRedirectLeader(write_response);
+    } while (io_.Now() < before + overall_timeout);
+
+    return TimedOut{};
+  }
+
+  BasicResult<TimedOut, ReadResponseT> SendReadRequest(ReadRequestT req) {
+    ReadRequest<ReadRequestT> read_req;
+    read_req.operation = req;
+
+    const Duration overall_timeout = io_.GetDefaultTimeout();
+    const Time before = io_.Now();
+
+    do {
+      spdlog::debug("client sending ReadRequest to Leader {}", leader_.ToString());
+
+      ResponseFuture<ReadResponse<ReadResponseT>> get_response_future =
+          io_.template Request<ReadRequest<ReadRequestT>, ReadResponse<ReadResponseT>>(leader_, read_req);
+
+      // receive response
+      ResponseResult<ReadResponse<ReadResponseT>> get_response_result = std::move(get_response_future).Wait();
+
+      if (get_response_result.HasError()) {
+        spdlog::debug("client timed out while trying to communicate with leader server {}", leader_.ToString());
+        return get_response_result.GetError();
+      }
+
+      ResponseEnvelope<ReadResponse<ReadResponseT>> &&get_response_envelope = std::move(get_response_result.GetValue());
+      ReadResponse<ReadResponseT> &&read_get_response = std::move(get_response_envelope.message);
+
+      if (read_get_response.success) {
+        return std::move(read_get_response.read_return);
+      }
+
+      PossiblyRedirectLeader(read_get_response);
+    } while (io_.Now() < before + overall_timeout);
+
+    return TimedOut{};
+  }
+};
+
+}  // namespace memgraph::io::rsm

src/io/rsm/shard_rsm.hpp

@@ -0,0 +1,155 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+/// The ShardRsm is a simple in-memory raft-backed kv store that can be used for simple testing
+/// and implementation of some query engine logic before storage engines are fully implemented.
+///
+/// To implement multiple read and write commands, change the StorageRead* and StorageWrite* requests
+/// and responses to a std::variant of the different options, and route them to specific handlers in
+/// the ShardRsm's Read and Apply methods. Remember that Read is called immediately when the Raft
+/// leader receives the request, and does not replicate anything over Raft. Apply is called only
+/// AFTER the StorageWriteRequest is replicated to a majority of Raft peers, and the result of calling
+/// ShardRsm::Apply(StorageWriteRequest) is returned to the client that submitted the request.
+
+#include <deque>
+#include <iostream>
+#include <map>
+#include <optional>
+#include <set>
+#include <thread>
+#include <vector>
+
+#include "coordinator/hybrid_logical_clock.hpp"
+#include "io/address.hpp"
+#include "io/rsm/raft.hpp"
+#include "storage/v3/id_types.hpp"
+#include "storage/v3/property_value.hpp"
+#include "utils/logging.hpp"
+
+namespace memgraph::io::rsm {
+
+using memgraph::coordinator::Hlc;
+using memgraph::storage::v3::LabelId;
+using memgraph::storage::v3::PropertyValue;
+
+using ShardRsmKey = std::vector<PropertyValue>;
+
+struct StorageWriteRequest {
+  LabelId label_id;
+  Hlc transaction_id;
+  ShardRsmKey key;
+  std::optional<int> value;
+};
+
+struct StorageWriteResponse {
+  bool shard_rsm_success;
+  std::optional<int> last_value;
+  // Only has a value if the given shard does not contain the requested key
+  std::optional<Hlc> latest_known_shard_map_version{std::nullopt};
+};
+
+struct StorageReadRequest {
+  LabelId label_id;
+  Hlc transaction_id;
+  ShardRsmKey key;
+};
+
+struct StorageReadResponse {
+  bool shard_rsm_success;
+  std::optional<int> value;
+  // Only has a value if the given shard does not contain the requested key
+  std::optional<Hlc> latest_known_shard_map_version{std::nullopt};
+};
+
+class ShardRsm {
+  std::map<ShardRsmKey, int> state_;
+  ShardRsmKey minimum_key_;
+  std::optional<ShardRsmKey> maximum_key_{std::nullopt};
+  Hlc shard_map_version_;
+
+  // The key is not located in this shard
+  bool IsKeyInRange(const ShardRsmKey &key) const {
+    if (maximum_key_) [[likely]] {
+      return (key >= minimum_key_ && key <= maximum_key_);
+    }
+    return key >= minimum_key_;
+  }
+
+ public:
+  StorageReadResponse Read(StorageReadRequest request) const {
+    StorageReadResponse ret;
+
+    if (!IsKeyInRange(request.key)) {
+      ret.latest_known_shard_map_version = shard_map_version_;
+      ret.shard_rsm_success = false;
+    } else if (state_.contains(request.key)) {
+      ret.value = state_.at(request.key);
+      ret.shard_rsm_success = true;
+    } else {
+      ret.shard_rsm_success = false;
+      ret.value = std::nullopt;
+    }
+    return ret;
+  }
+
+  StorageWriteResponse Apply(StorageWriteRequest request) {
+    StorageWriteResponse ret;
+
+    // Key is outside the prohibited range
+    if (!IsKeyInRange(request.key)) {
+      ret.latest_known_shard_map_version = shard_map_version_;
+      ret.shard_rsm_success = false;
+    }
+    // Key exist
+    else if (state_.contains(request.key)) {
+      auto &val = state_[request.key];
+
+      /*
+       *   Delete
+       */
+      if (!request.value) {
+        ret.shard_rsm_success = true;
+        ret.last_value = val;
+        state_.erase(state_.find(request.key));
+      }
+
+      /*
+       *   Update
+       */
+      // Does old_value match?
+      if (request.value == val) {
+        ret.last_value = val;
+        ret.shard_rsm_success = true;
+
+        val = request.value.value();
+
+      } else {
+        ret.last_value = val;
+        ret.shard_rsm_success = false;
+      }
+    }
+    /*
+     *   Create
+     */
+    else {
+      ret.last_value = std::nullopt;
+      ret.shard_rsm_success = true;
+
+      state_.emplace(request.key, request.value.value());
+    }
+
+    return ret;
+  }
+};
+
+}  // namespace memgraph::io::rsm

src/io/simulator/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(io_simulator_sources
+    simulator_handle.cpp)
+
+find_package(fmt REQUIRED)
+find_package(Threads REQUIRED)
+
+add_library(mg-io-simulator STATIC ${io_simulator_sources})
+target_link_libraries(mg-io-simulator stdc++fs Threads::Threads fmt::fmt mg-utils)

src/io/simulator/simulator.hpp

@@ -0,0 +1,51 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <memory>
+#include <random>
+
+#include "io/address.hpp"
+#include "io/simulator/simulator_config.hpp"
+#include "io/simulator/simulator_handle.hpp"
+#include "io/simulator/simulator_transport.hpp"
+
+namespace memgraph::io::simulator {
+class Simulator {
+  std::mt19937 rng_;
+  std::shared_ptr<SimulatorHandle> simulator_handle_;
+  uint16_t auto_port_ = 0;
+
+ public:
+  explicit Simulator(SimulatorConfig config)
+      : rng_(std::mt19937{config.rng_seed}), simulator_handle_{std::make_shared<SimulatorHandle>(config)} {}
+
+  void ShutDown() { simulator_handle_->ShutDown(); }
+
+  Io<SimulatorTransport> RegisterNew() {
+    Address address = Address::TestAddress(auto_port_++);
+    return Register(address);
+  }
+
+  Io<SimulatorTransport> Register(Address address) {
+    std::uniform_int_distribution<uint64_t> seed_distrib;
+    uint64_t seed = seed_distrib(rng_);
+    return Io{SimulatorTransport{simulator_handle_, address, seed}, address};
+  }
+
+  void IncrementServerCountAndWaitForQuiescentState(Address address) {
+    simulator_handle_->IncrementServerCountAndWaitForQuiescentState(address);
+  }
+
+  SimulatorStats Stats() { return simulator_handle_->Stats(); }
+};
+};  // namespace memgraph::io::simulator

src/io/simulator/simulator_config.hpp

@@ -0,0 +1,30 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <chrono>
+
+#include "io/time.hpp"
+
+namespace memgraph::io::simulator {
+
+using memgraph::io::Time;
+
+struct SimulatorConfig {
+  uint8_t drop_percent = 0;
+  bool perform_timeouts = false;
+  bool scramble_messages = true;
+  uint64_t rng_seed = 0;
+  Time start_time = Time::min();
+  Time abort_time = Time::max();
+};
+};  // namespace memgraph::io::simulator

src/io/simulator/simulator_handle.cpp

@@ -0,0 +1,142 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "io/simulator/simulator_handle.hpp"
+#include "io/address.hpp"
+#include "io/errors.hpp"
+#include "io/simulator/simulator_config.hpp"
+#include "io/simulator/simulator_stats.hpp"
+#include "io/time.hpp"
+#include "io/transport.hpp"
+
+namespace memgraph::io::simulator {
+
+using memgraph::io::Duration;
+using memgraph::io::Time;
+
+void SimulatorHandle::ShutDown() {
+  std::unique_lock<std::mutex> lock(mu_);
+  should_shut_down_ = true;
+  cv_.notify_all();
+}
+
+bool SimulatorHandle::ShouldShutDown() const {
+  std::unique_lock<std::mutex> lock(mu_);
+  return should_shut_down_;
+}
+
+void SimulatorHandle::IncrementServerCountAndWaitForQuiescentState(Address address) {
+  std::unique_lock<std::mutex> lock(mu_);
+  server_addresses_.insert(address);
+
+  while (true) {
+    const size_t blocked_servers = blocked_on_receive_.size();
+
+    const bool all_servers_blocked = blocked_servers == server_addresses_.size();
+
+    if (all_servers_blocked) {
+      return;
+    }
+
+    cv_.wait(lock);
+  }
+}
+
+bool SimulatorHandle::MaybeTickSimulator() {
+  std::unique_lock<std::mutex> lock(mu_);
+
+  const size_t blocked_servers = blocked_on_receive_.size();
+
+  if (blocked_servers < server_addresses_.size()) {
+    // we only need to advance the simulator when all
+    // servers have reached a quiescent state, blocked
+    // on their own futures or receive methods.
+    return false;
+  }
+
+  stats_.simulator_ticks++;
+
+  cv_.notify_all();
+
+  TimeoutPromisesPastDeadline();
+
+  if (in_flight_.empty()) {
+    // return early here because there are no messages to schedule
+
+    // We tick the clock forward when all servers are blocked but
+    // there are no in-flight messages to schedule delivery of.
+    std::poisson_distribution<> time_distrib(50);
+    Duration clock_advance = std::chrono::microseconds{time_distrib(rng_)};
+    cluster_wide_time_microseconds_ += clock_advance;
+
+    MG_ASSERT(cluster_wide_time_microseconds_ < config_.abort_time,
+              "Cluster has executed beyond its configured abort_time, and something may be failing to make progress "
+              "in an expected amount of time.");
+    return true;
+  }
+
+  if (config_.scramble_messages) {
+    // scramble messages
+    std::uniform_int_distribution<size_t> swap_distrib(0, in_flight_.size() - 1);
+    const size_t swap_index = swap_distrib(rng_);
+    std::swap(in_flight_[swap_index], in_flight_.back());
+  }
+
+  auto [to_address, opaque_message] = std::move(in_flight_.back());
+  in_flight_.pop_back();
+
+  std::uniform_int_distribution<int> drop_distrib(0, 99);
+  const int drop_threshold = drop_distrib(rng_);
+  const bool should_drop = drop_threshold < config_.drop_percent;
+
+  if (should_drop) {
+    stats_.dropped_messages++;
+  }
+
+  PromiseKey promise_key{.requester_address = to_address,
+                         .request_id = opaque_message.request_id,
+                         .replier_address = opaque_message.from_address};
+
+  if (promises_.contains(promise_key)) {
+    // complete waiting promise if it's there
+    DeadlineAndOpaquePromise dop = std::move(promises_.at(promise_key));
+    promises_.erase(promise_key);
+
+    const bool normal_timeout = config_.perform_timeouts && (dop.deadline < cluster_wide_time_microseconds_);
+
+    if (should_drop || normal_timeout) {
+      stats_.timed_out_requests++;
+      dop.promise.TimeOut();
+    } else {
+      stats_.total_responses++;
+      dop.promise.Fill(std::move(opaque_message));
+    }
+  } else if (should_drop) {
+    // don't add it anywhere, let it drop
+  } else {
+    // add to can_receive_ if not
+    const auto &[om_vec, inserted] = can_receive_.try_emplace(to_address, std::vector<OpaqueMessage>());
+    om_vec->second.emplace_back(std::move(opaque_message));
+  }
+
+  return true;
+}
+
+Time SimulatorHandle::Now() const {
+  std::unique_lock<std::mutex> lock(mu_);
+  return cluster_wide_time_microseconds_;
+}
+
+SimulatorStats SimulatorHandle::Stats() {
+  std::unique_lock<std::mutex> lock(mu_);
+  return stats_;
+}
+}  // namespace memgraph::io::simulator

src/io/simulator/simulator_handle.hpp

@@ -0,0 +1,177 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <any>
+#include <compare>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <optional>
+#include <set>
+#include <utility>
+#include <variant>
+#include <vector>
+
+#include "io/address.hpp"
+#include "io/errors.hpp"
+#include "io/message_conversion.hpp"
+#include "io/simulator/simulator_config.hpp"
+#include "io/simulator/simulator_stats.hpp"
+#include "io/time.hpp"
+#include "io/transport.hpp"
+
+namespace memgraph::io::simulator {
+
+class SimulatorHandle {
+  mutable std::mutex mu_{};
+  mutable std::condition_variable cv_;
+
+  // messages that have not yet been scheduled or dropped
+  std::vector<std::pair<Address, OpaqueMessage>> in_flight_;
+
+  // the responses to requests that are being waited on
+  std::map<PromiseKey, DeadlineAndOpaquePromise> promises_;
+
+  // messages that are sent to servers that may later receive them
+  std::map<Address, std::vector<OpaqueMessage>> can_receive_;
+
+  Time cluster_wide_time_microseconds_;
+  bool should_shut_down_ = false;
+  SimulatorStats stats_;
+  std::set<Address> blocked_on_receive_;
+  std::set<Address> server_addresses_;
+  std::mt19937 rng_;
+  SimulatorConfig config_;
+
+  void TimeoutPromisesPastDeadline() {
+    const Time now = cluster_wide_time_microseconds_;
+    for (auto it = promises_.begin(); it != promises_.end();) {
+      auto &[promise_key, dop] = *it;
+      if (dop.deadline < now) {
+        spdlog::info("timing out request from requester {} to replier {}.", promise_key.requester_address.ToString(),
+                     promise_key.replier_address.ToString());
+        std::move(dop).promise.TimeOut();
+        it = promises_.erase(it);
+
+        stats_.timed_out_requests++;
+      } else {
+        ++it;
+      }
+    }
+  }
+
+ public:
+  explicit SimulatorHandle(SimulatorConfig config)
+      : cluster_wide_time_microseconds_(config.start_time), rng_(config.rng_seed), config_(config) {}
+
+  void IncrementServerCountAndWaitForQuiescentState(Address address);
+
+  /// This method causes most of the interesting simulation logic to happen, wrt network behavior.
+  /// It checks to see if all background "server" threads are blocked on new messages, and if so,
+  /// it will decide whether to drop, reorder, or deliver in-flight messages based on the SimulatorConfig
+  /// that was used to create the Simulator.
+  bool MaybeTickSimulator();
+
+  void ShutDown();
+
+  bool ShouldShutDown() const;
+
+  template <Message Request, Message Response>
+  void SubmitRequest(Address to_address, Address from_address, RequestId request_id, Request &&request,
+                     Duration timeout, ResponsePromise<Response> &&promise) {
+    std::unique_lock<std::mutex> lock(mu_);
+
+    const Time deadline = cluster_wide_time_microseconds_ + timeout;
+
+    std::any message(request);
+    OpaqueMessage om{.to_address = to_address,
+                     .from_address = from_address,
+                     .request_id = request_id,
+                     .message = std::move(message)};
+    in_flight_.emplace_back(std::make_pair(to_address, std::move(om)));
+
+    PromiseKey promise_key{.requester_address = from_address, .request_id = request_id, .replier_address = to_address};
+    OpaquePromise opaque_promise(std::move(promise).ToUnique());
+    DeadlineAndOpaquePromise dop{.deadline = deadline, .promise = std::move(opaque_promise)};
+    promises_.emplace(std::move(promise_key), std::move(dop));
+
+    stats_.total_messages++;
+    stats_.total_requests++;
+
+    cv_.notify_all();
+  }
+
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) RequestResult<Ms...> Receive(const Address &receiver, Duration timeout) {
+    std::unique_lock<std::mutex> lock(mu_);
+
+    blocked_on_receive_.emplace(receiver);
+
+    const Time deadline = cluster_wide_time_microseconds_ + timeout;
+
+    while (!should_shut_down_ && (cluster_wide_time_microseconds_ < deadline)) {
+      if (can_receive_.contains(receiver)) {
+        std::vector<OpaqueMessage> &can_rx = can_receive_.at(receiver);
+        if (!can_rx.empty()) {
+          OpaqueMessage message = std::move(can_rx.back());
+          can_rx.pop_back();
+
+          // TODO(tyler) search for item in can_receive_ that matches the desired types, rather
+          // than asserting that the last item in can_rx matches.
+          auto m_opt = std::move(message).Take<Ms...>();
+
+          blocked_on_receive_.erase(receiver);
+
+          return std::move(m_opt).value();
+        }
+      }
+
+      lock.unlock();
+      bool made_progress = MaybeTickSimulator();
+      lock.lock();
+      if (!should_shut_down_ && !made_progress) {
+        cv_.wait(lock);
+      }
+    }
+
+    blocked_on_receive_.erase(receiver);
+
+    return TimedOut{};
+  }
+
+  template <Message M>
+  void Send(Address to_address, Address from_address, RequestId request_id, M message) {
+    std::unique_lock<std::mutex> lock(mu_);
+    std::any message_any(std::move(message));
+    OpaqueMessage om{.to_address = to_address,
+                     .from_address = from_address,
+                     .request_id = request_id,
+                     .message = std::move(message_any)};
+    in_flight_.emplace_back(std::make_pair(std::move(to_address), std::move(om)));
+
+    stats_.total_messages++;
+
+    cv_.notify_all();
+  }
+
+  Time Now() const;
+
+  template <class D = std::poisson_distribution<>, class Return = uint64_t>
+  Return Rand(D distrib) {
+    std::unique_lock<std::mutex> lock(mu_);
+    return distrib(rng_);
+  }
+
+  SimulatorStats Stats();
+};
+};  // namespace memgraph::io::simulator

src/io/simulator/simulator_stats.hpp

@@ -0,0 +1,25 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <cstdint>
+
+namespace memgraph::io::simulator {
+struct SimulatorStats {
+  uint64_t total_messages = 0;
+  uint64_t dropped_messages = 0;
+  uint64_t timed_out_requests = 0;
+  uint64_t total_requests = 0;
+  uint64_t total_responses = 0;
+  uint64_t simulator_ticks = 0;
+};
+};  // namespace memgraph::io::simulator

src/io/simulator/simulator_transport.hpp

@@ -0,0 +1,67 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <memory>
+#include <utility>
+
+#include "io/address.hpp"
+#include "io/simulator/simulator_handle.hpp"
+#include "io/time.hpp"
+
+namespace memgraph::io::simulator {
+
+using memgraph::io::Duration;
+using memgraph::io::Time;
+
+class SimulatorTransport {
+  std::shared_ptr<SimulatorHandle> simulator_handle_;
+  const Address address_;
+  std::mt19937 rng_;
+
+ public:
+  SimulatorTransport(std::shared_ptr<SimulatorHandle> simulator_handle, Address address, uint64_t seed)
+      : simulator_handle_(simulator_handle), address_(address), rng_(std::mt19937{seed}) {}
+
+  template <Message RequestT, Message ResponseT>
+  ResponseFuture<ResponseT> Request(Address to_address, Address from_address, uint64_t request_id, RequestT request,
+                                    Duration timeout) {
+    std::function<bool()> maybe_tick_simulator = [this] { return simulator_handle_->MaybeTickSimulator(); };
+    auto [future, promise] =
+        memgraph::io::FuturePromisePairWithNotifier<ResponseResult<ResponseT>>(maybe_tick_simulator);
+
+    simulator_handle_->SubmitRequest(to_address, from_address, request_id, std::move(request), timeout,
+                                     std::move(promise));
+
+    return std::move(future);
+  }
+
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) RequestResult<Ms...> Receive(Address receiver_address, Duration timeout) {
+    return simulator_handle_->template Receive<Ms...>(receiver_address, timeout);
+  }
+
+  template <Message M>
+  void Send(Address to_address, Address from_address, uint64_t request_id, M message) {
+    return simulator_handle_->template Send<M>(to_address, from_address, request_id, message);
+  }
+
+  Time Now() const { return simulator_handle_->Now(); }
+
+  bool ShouldShutDown() const { return simulator_handle_->ShouldShutDown(); }
+
+  template <class D = std::poisson_distribution<>, class Return = uint64_t>
+  Return Rand(D distrib) {
+    return distrib(rng_);
+  }
+};
+};  // namespace memgraph::io::simulator

src/io/time.hpp

@@ -0,0 +1,21 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <chrono>
+
+namespace memgraph::io {
+
+using Duration = std::chrono::microseconds;
+using Time = std::chrono::time_point<std::chrono::system_clock, Duration>;
+
+}  // namespace memgraph::io

src/io/transport.hpp

@@ -0,0 +1,144 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <chrono>
+#include <concepts>
+#include <random>
+#include <variant>
+
+#include "io/address.hpp"
+#include "io/errors.hpp"
+#include "io/future.hpp"
+#include "io/time.hpp"
+#include "utils/result.hpp"
+
+namespace memgraph::io {
+
+using memgraph::utils::BasicResult;
+
+// TODO(tyler) ensure that Message continues to represent
+// reasonable constraints around message types over time,
+// as we adapt things to use Thrift-generated message types.
+template <typename T>
+concept Message = std::same_as<T, std::decay_t<T>>;
+
+using RequestId = uint64_t;
+
+template <Message M>
+struct ResponseEnvelope {
+  M message;
+  RequestId request_id;
+  Address to_address;
+  Address from_address;
+};
+
+template <Message M>
+using ResponseResult = BasicResult<TimedOut, ResponseEnvelope<M>>;
+
+template <Message M>
+using ResponseFuture = memgraph::io::Future<ResponseResult<M>>;
+
+template <Message M>
+using ResponsePromise = memgraph::io::Promise<ResponseResult<M>>;
+
+template <Message... Ms>
+struct RequestEnvelope {
+  std::variant<Ms...> message;
+  RequestId request_id;
+  Address to_address;
+  Address from_address;
+};
+
+template <Message... Ms>
+using RequestResult = BasicResult<TimedOut, RequestEnvelope<Ms...>>;
+
+template <typename I>
+class Io {
+  I implementation_;
+  Address address_;
+  RequestId request_id_counter_ = 0;
+  Duration default_timeout_ = std::chrono::microseconds{100000};
+
+ public:
+  Io(I io, Address address) : implementation_(io), address_(address) {}
+
+  /// Set the default timeout for all requests that are issued
+  /// without an explicit timeout set.
+  void SetDefaultTimeout(Duration timeout) { default_timeout_ = timeout; }
+
+  /// Returns the current default timeout for this Io instance.
+  Duration GetDefaultTimeout() { return default_timeout_; }
+
+  /// Issue a request with an explicit timeout in microseconds provided. This tends to be used by clients.
+  template <Message RequestT, Message ResponseT>
+  ResponseFuture<ResponseT> RequestWithTimeout(Address address, RequestT request, Duration timeout) {
+    const RequestId request_id = ++request_id_counter_;
+    const Address from_address = address_;
+    return implementation_.template Request<RequestT, ResponseT>(address, from_address, request_id, request, timeout);
+  }
+
+  /// Issue a request that times out after the default timeout. This tends
+  /// to be used by clients.
+  template <Message RequestT, Message ResponseT>
+  ResponseFuture<ResponseT> Request(Address to_address, RequestT request) {
+    const RequestId request_id = ++request_id_counter_;
+    const Duration timeout = default_timeout_;
+    const Address from_address = address_;
+    return implementation_.template Request<RequestT, ResponseT>(to_address, from_address, request_id,
+                                                                 std::move(request), timeout);
+  }
+
+  /// Wait for an explicit number of microseconds for a request of one of the
+  /// provided types to arrive. This tends to be used by servers.
+  template <Message... Ms>
+  RequestResult<Ms...> ReceiveWithTimeout(Duration timeout) {
+    return implementation_.template Receive<Ms...>(address_, timeout);
+  }
+
+  /// Wait the default number of microseconds for a request of one of the
+  /// provided types to arrive. This tends to be used by servers.
+  template <Message... Ms>
+  requires(sizeof...(Ms) > 0) RequestResult<Ms...> Receive() {
+    const Duration timeout = default_timeout_;
+    return implementation_.template Receive<Ms...>(address_, timeout);
+  }
+
+  /// Send a message in a best-effort fashion. This is used for messaging where
+  /// responses are not necessarily expected, and for servers to respond to requests.
+  /// If you need reliable delivery, this must be built on-top. TCP is not enough for most use cases.
+  template <Message M>
+  void Send(Address to_address, RequestId request_id, M message) {
+    Address from_address = address_;
+    return implementation_.template Send<M>(to_address, from_address, request_id, std::move(message));
+  }
+
+  /// The current system time. This time source should be preferred over any other,
+  /// because it lets us deterministically control clocks from tests for making
+  /// things like timeouts deterministic.
+  Time Now() const { return implementation_.Now(); }
+
+  /// Returns true if the system should shut-down.
+  bool ShouldShutDown() const { return implementation_.ShouldShutDown(); }
+
+  /// Returns a random number within the specified distribution.
+  template <class D = std::poisson_distribution<>, class Return = uint64_t>
+  Return Rand(D distrib) {
+    return implementation_.template Rand<D, Return>(distrib);
+  }
+
+  Address GetAddress() { return address_; }
+  void SetAddress(Address address) { address_ = address; }
+
+  Io<I> ForkLocal() { return Io(implementation_, address_.ForkUniqueAddress()); }
+};
+};  // namespace memgraph::io

src/machine_manager/machine_config.hpp

@@ -0,0 +1,42 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <boost/asio/ip/tcp.hpp>
+#include "io/address.hpp"
+#include "storage/v3/property_value.hpp"
+#include "storage/v3/schemas.hpp"
+
+namespace memgraph::machine_manager {
+
+using memgraph::io::Address;
+using memgraph::storage::v3::SchemaProperty;
+using CompoundKey = std::vector<memgraph::storage::v3::PropertyValue>;
+
+struct InitialLabelSpace {
+  std::string label_name;
+  std::vector<SchemaProperty> schema;
+  size_t replication_factor;
+  std::vector<CompoundKey> split_points;
+};
+
+struct MachineConfig {
+  std::vector<InitialLabelSpace> initial_label_spaces;
+  std::vector<Address> coordinator_addresses;
+  bool is_storage;
+  bool is_coordinator;
+  bool is_query_engine;
+  boost::asio::ip::address listen_ip;
+  uint16_t listen_port;
+};
+
+}  // namespace memgraph::machine_manager

src/machine_manager/machine_manager.hpp

@@ -0,0 +1,177 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <coordinator/coordinator_rsm.hpp>
+#include <io/message_conversion.hpp>
+#include <io/messages.hpp>
+#include <io/rsm/rsm_client.hpp>
+#include <io/time.hpp>
+#include <machine_manager/machine_config.hpp>
+#include <storage/v3/shard_manager.hpp>
+
+namespace memgraph::machine_manager {
+
+using memgraph::coordinator::Coordinator;
+using memgraph::coordinator::CoordinatorReadRequests;
+using memgraph::coordinator::CoordinatorReadResponses;
+using memgraph::coordinator::CoordinatorRsm;
+using memgraph::coordinator::CoordinatorWriteRequests;
+using memgraph::coordinator::CoordinatorWriteResponses;
+using memgraph::io::ConvertVariant;
+using memgraph::io::Duration;
+using memgraph::io::RequestId;
+using memgraph::io::Time;
+using memgraph::io::messages::CoordinatorMessages;
+using memgraph::io::messages::ShardManagerMessages;
+using memgraph::io::messages::ShardMessages;
+using memgraph::io::messages::StorageReadRequest;
+using memgraph::io::messages::StorageWriteRequest;
+using memgraph::io::rsm::AppendRequest;
+using memgraph::io::rsm::AppendResponse;
+using memgraph::io::rsm::ReadRequest;
+using memgraph::io::rsm::VoteRequest;
+using memgraph::io::rsm::VoteResponse;
+using memgraph::io::rsm::WriteRequest;
+using memgraph::io::rsm::WriteResponse;
+using memgraph::storage::v3::ShardManager;
+
+/// The MachineManager is responsible for:
+/// * starting the entire system and ensuring that high-level
+///   operational requirements continue to be met
+/// * acting as a machine's single caller of Io::Receive
+/// * routing incoming messages from the Io interface to the
+///   appropriate Coordinator or to the StorageManager
+///   (it's not necessary to route anything in this layer
+///   to the query engine because the query engine only
+///   communicates using higher-level Futures that will
+///   be filled immediately when the response comes in
+///   at the lower-level transport layer.
+///
+/// Every storage engine has exactly one RsmEngine.
+template <typename IoImpl>
+class MachineManager {
+  io::Io<IoImpl> io_;
+  MachineConfig config_;
+  CoordinatorRsm<IoImpl> coordinator_;
+  ShardManager<IoImpl> shard_manager_;
+  Time next_cron_;
+
+ public:
+  // TODO initialize ShardManager with "real" coordinator addresses instead of io.GetAddress
+  // which is only true for single-machine config.
+  MachineManager(io::Io<IoImpl> io, MachineConfig config, Coordinator coordinator)
+      : io_(io),
+        config_(config),
+        coordinator_{std::move(io.ForkLocal()), {}, std::move(coordinator)},
+        shard_manager_(ShardManager{io.ForkLocal(), coordinator_.GetAddress()}) {}
+
+  Address CoordinatorAddress() { return coordinator_.GetAddress(); }
+
+  void Run() {
+    while (!io_.ShouldShutDown()) {
+      const auto now = io_.Now();
+
+      if (now >= next_cron_) {
+        next_cron_ = Cron();
+      }
+
+      Duration receive_timeout = next_cron_ - now;
+
+      // Note: this parameter pack must be kept in-sync with the ReceiveWithTimeout parameter pack below
+      using AllMessages =
+          std::variant<ReadRequest<CoordinatorReadRequests>, AppendRequest<CoordinatorWriteRequests>, AppendResponse,
+                       WriteRequest<CoordinatorWriteRequests>, VoteRequest, VoteResponse,
+                       WriteResponse<CoordinatorWriteResponses>, ReadRequest<StorageReadRequest>,
+                       AppendRequest<StorageWriteRequest>, WriteRequest<StorageWriteRequest>>;
+
+      spdlog::info("MM waiting on Receive");
+
+      // Note: this parameter pack must be kept in-sync with the AllMessages parameter pack above
+      auto request_result = io_.template ReceiveWithTimeout<
+          ReadRequest<CoordinatorReadRequests>, AppendRequest<CoordinatorWriteRequests>, AppendResponse,
+          WriteRequest<CoordinatorWriteRequests>, VoteRequest, VoteResponse, WriteResponse<CoordinatorWriteResponses>,
+          ReadRequest<StorageReadRequest>, AppendRequest<StorageWriteRequest>, WriteRequest<StorageWriteRequest>>(
+          receive_timeout);
+
+      if (request_result.HasError()) {
+        // time to do Cron
+        spdlog::info("MM got timeout");
+        continue;
+      }
+
+      auto &&request_envelope = std::move(request_result.GetValue());
+
+      spdlog::info("MM got message to {}", request_envelope.to_address.ToString());
+
+      // If message is for the coordinator, cast it to subset and pass it to the coordinator
+      bool to_coordinator = coordinator_.GetAddress() == request_envelope.to_address;
+      spdlog::info("coordinator: {}", coordinator_.GetAddress().ToString());
+      if (to_coordinator) {
+        std::optional<CoordinatorMessages> conversion_attempt =
+            ConvertVariant<AllMessages, ReadRequest<CoordinatorReadRequests>, AppendRequest<CoordinatorWriteRequests>,
+                           AppendResponse, WriteRequest<CoordinatorWriteRequests>, VoteRequest, VoteResponse>(
+                std::move(request_envelope.message));
+
+        MG_ASSERT(conversion_attempt.has_value(), "coordinator message conversion failed");
+
+        spdlog::info("got coordinator message");
+
+        CoordinatorMessages &&cm = std::move(conversion_attempt.value());
+
+        coordinator_.Handle(std::forward<CoordinatorMessages>(cm), request_envelope.request_id,
+                            request_envelope.from_address);
+        continue;
+      }
+
+      bool to_sm = shard_manager_.GetAddress() == request_envelope.to_address;
+      spdlog::info("smm: {}", shard_manager_.GetAddress().ToString());
+      if (to_sm) {
+        std::optional<ShardManagerMessages> conversion_attempt =
+            ConvertVariant<AllMessages, WriteResponse<CoordinatorWriteResponses>>(std::move(request_envelope.message));
+
+        MG_ASSERT(conversion_attempt.has_value(), "shard manager message conversion failed");
+
+        spdlog::info("got shard manager message");
+
+        ShardManagerMessages &&smm = std::move(conversion_attempt.value());
+        shard_manager_.Receive(std::forward<ShardManagerMessages>(smm), request_envelope.request_id,
+                               request_envelope.from_address);
+        continue;
+      }
+
+      // treat this as a message to a specific shard rsm and cast it accordingly
+
+      std::optional<ShardMessages> conversion_attempt =
+          ConvertVariant<AllMessages, ReadRequest<StorageReadRequest>, AppendRequest<StorageWriteRequest>,
+                         AppendResponse, WriteRequest<StorageWriteRequest>, VoteRequest, VoteResponse>(
+              std::move(request_envelope.message));
+
+      MG_ASSERT(conversion_attempt.has_value(), "shard rsm message conversion failed for {}",
+                request_envelope.to_address.ToString());
+
+      spdlog::info("got shard rsm message");
+
+      ShardMessages &&sm = std::move(conversion_attempt.value());
+      shard_manager_.Route(std::forward<ShardMessages>(sm), request_envelope.request_id, request_envelope.to_address,
+                           request_envelope.from_address);
+    }
+  }
+
+ private:
+  Time Cron() {
+    spdlog::info("running MachineManager::Cron, address {}", io_.GetAddress().ToString());
+    return shard_manager_.Cron();
+  }
+};
+
+}  // namespace memgraph::machine_manager

src/memgraph.cpp

@@ -164,6 +164,8 @@ DEFINE_string(bolt_server_name_for_init, "",
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
 DEFINE_string(data_directory, "mg_data", "Path to directory in which to save all permanent data.");
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_HIDDEN_string(log_link_basename, "", "Basename used for symlink creation to the last log file.");
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
 DEFINE_uint64(memory_warning_threshold, 1024,
               "Memory warning threshold, in MB. If Memgraph detects there is "
               "less available RAM it will log a warning. Set to 0 to "
@@ -214,6 +216,11 @@ DEFINE_bool(telemetry_enabled, false,
             "the database runtime (vertex and edge counts and resource usage) "
             "to allow for easier improvement of the product.");
 
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+DEFINE_bool(storage_restore_replicas_on_startup, true,
+            "Controls replicas should be restored automatically.");  // TODO(42jeremy) this must be removed once T0835
+                                                                     // is implemented.
+
 // Streams flags
 // NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
 DEFINE_uint32(
@@ -347,8 +354,7 @@ DEFINE_VALIDATED_string(query_modules_directory, "",
                         });
 
 // Logging flags
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_HIDDEN_bool(also_log_to_stderr, false, "Log messages go to stderr in addition to logfiles");
+DEFINE_bool(also_log_to_stderr, false, "Log messages go to stderr in addition to logfiles");
 DEFINE_string(log_file, "", "Path to where the log should be stored.");
 
 namespace {
@@ -428,9 +434,9 @@ void AddLoggerSink(spdlog::sink_ptr new_sink) {
 }  // namespace
 
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_HIDDEN_string(license_key, "", "License key for Memgraph Enterprise.");
+DEFINE_string(license_key, "", "License key for Memgraph Enterprise.");
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_HIDDEN_string(organization_name, "", "Organization name.");
+DEFINE_string(organization_name, "", "Organization name.");
 
 /// Encapsulates Dbms and Interpreter that are passed through the network server
 /// and worker to the session.
@@ -900,8 +906,6 @@ class BoltSession final : public memgraph::communication::bolt::Session<memgraph
       // Wrap QueryException into ClientError, because we want to allow the
       // client to fix their query.
       throw memgraph::communication::bolt::ClientError(e.what());
-    } catch (const memgraph::query::ReplicationException &e) {
-      throw memgraph::communication::bolt::ClientError(e.what());
     }
   }
 
@@ -1197,7 +1201,7 @@ int main(int argc, char **argv) {
                      .wal_file_size_kibibytes = FLAGS_storage_wal_file_size_kib,
                      .wal_file_flush_every_n_tx = FLAGS_storage_wal_file_flush_every_n_tx,
                      .snapshot_on_exit = FLAGS_storage_snapshot_on_exit,
-                     .restore_replicas_on_startup = true},
+                     .restore_replicas_on_startup = FLAGS_storage_restore_replicas_on_startup},
       .transaction = {.isolation_level = ParseIsolationLevel()}};
   if (FLAGS_storage_snapshot_interval_sec == 0) {
     if (FLAGS_storage_wal_enabled) {

src/parser/CMakeLists.txt

@@ -0,0 +1,41 @@
+## Generate Antlr openCypher parser
+
+set(opencypher_frontend ${CMAKE_CURRENT_SOURCE_DIR}/opencypher)
+set(opencypher_generated ${opencypher_frontend}/generated)
+set(opencypher_lexer_grammar ${opencypher_frontend}/grammar/MemgraphCypherLexer.g4)
+set(opencypher_parser_grammar ${opencypher_frontend}/grammar/MemgraphCypher.g4)
+
+set(antlr_opencypher_generated_src
+    ${opencypher_generated}/MemgraphCypherLexer.cpp
+    ${opencypher_generated}/MemgraphCypher.cpp
+    ${opencypher_generated}/MemgraphCypherBaseVisitor.cpp
+    ${opencypher_generated}/MemgraphCypherVisitor.cpp
+)
+set(antlr_opencypher_generated_include
+    ${opencypher_generated}/MemgraphCypherLexer.h
+    ${opencypher_generated}/MemgraphCypher.h
+    ${opencypher_generated}/MemgraphCypherBaseVisitor.h
+    ${opencypher_generated}/MemgraphCypherVisitor.h
+)
+
+add_custom_command(
+    OUTPUT ${antlr_opencypher_generated_src} ${antlr_opencypher_generated_include}
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${opencypher_generated}
+    COMMAND
+        java -jar ${CMAKE_SOURCE_DIR}/libs/antlr-4.10.1-complete.jar
+            -Dlanguage=Cpp -visitor -package antlropencypher
+            -o ${opencypher_generated}
+            ${opencypher_lexer_grammar} ${opencypher_parser_grammar}
+    WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
+    DEPENDS
+        ${opencypher_lexer_grammar} ${opencypher_parser_grammar}
+        ${opencypher_frontend}/grammar/CypherLexer.g4
+        ${opencypher_frontend}/grammar/Cypher.g4)
+
+add_custom_target(generated_opencypher_parser
+    DEPENDS ${antlr_opencypher_generated_src} ${antlr_opencypher_generated_include})
+
+add_library(mg-parser STATIC ${antlr_opencypher_generated_src})
+add_dependencies(mg-parser generated_opencypher_parser)
+target_include_directories(mg-parser PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+target_link_libraries(mg-parser antlr4)

src/parser/opencypher/grammar/Cypher.g4

@@ -0,0 +1,391 @@
+/*
+ * Copyright (c) 2015-2016 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+parser grammar Cypher;
+
+options { tokenVocab=CypherLexer; }
+
+cypher : statement ';'? EOF ;
+
+statement : query ;
+
+query : cypherQuery
+      | indexQuery
+      | explainQuery
+      | profileQuery
+      | infoQuery
+      | constraintQuery
+      ;
+
+constraintQuery : ( CREATE | DROP ) CONSTRAINT ON constraint ;
+
+constraint : '(' nodeName=variable ':' labelName ')' ASSERT EXISTS '(' constraintPropertyList ')'
+           | '(' nodeName=variable ':' labelName ')' ASSERT constraintPropertyList IS UNIQUE
+           | '(' nodeName=variable ':' labelName ')' ASSERT '(' constraintPropertyList ')' IS NODE KEY
+           ;
+
+constraintPropertyList : variable propertyLookup ( ',' variable propertyLookup )* ;
+
+storageInfo : STORAGE INFO ;
+
+indexInfo : INDEX INFO ;
+
+constraintInfo : CONSTRAINT INFO ;
+
+infoQuery : SHOW ( storageInfo | indexInfo | constraintInfo ) ;
+
+explainQuery : EXPLAIN cypherQuery ;
+
+profileQuery : PROFILE cypherQuery ;
+
+cypherQuery : singleQuery ( cypherUnion )* ( queryMemoryLimit )? ;
+
+indexQuery : createIndex | dropIndex;
+
+singleQuery : clause ( clause )* ;
+
+cypherUnion : ( UNION ALL singleQuery )
+            | ( UNION singleQuery )
+            ;
+
+clause : cypherMatch
+       | unwind
+       | merge
+       | create
+       | set
+       | cypherDelete
+       | remove
+       | with
+       | cypherReturn
+       | callProcedure
+       ;
+
+cypherMatch : OPTIONAL? MATCH pattern where? ;
+
+unwind : UNWIND expression AS variable ;
+
+merge : MERGE patternPart ( mergeAction )* ;
+
+mergeAction : ( ON MATCH set )
+            | ( ON CREATE set )
+            ;
+
+create : CREATE pattern ;
+
+set : SET setItem ( ',' setItem )* ;
+
+setItem : ( propertyExpression '=' expression )
+        | ( variable '=' expression )
+        | ( variable '+=' expression )
+        | ( variable nodeLabels )
+        ;
+
+cypherDelete : DETACH? DELETE expression ( ',' expression )* ;
+
+remove : REMOVE removeItem ( ',' removeItem )* ;
+
+removeItem : ( variable nodeLabels )
+           | propertyExpression
+           ;
+
+with : WITH ( DISTINCT )? returnBody ( where )? ;
+
+cypherReturn : RETURN ( DISTINCT )? returnBody ;
+
+callProcedure : CALL procedureName '(' ( expression ( ',' expression )* )? ')' ( procedureMemoryLimit )? ( yieldProcedureResults )? ;
+
+procedureName : symbolicName ( '.' symbolicName )* ;
+
+yieldProcedureResults : YIELD ( '*' | ( procedureResult ( ',' procedureResult )* ) ) ;
+
+memoryLimit : MEMORY ( UNLIMITED | LIMIT literal ( MB | KB ) ) ;
+
+queryMemoryLimit : QUERY memoryLimit ;
+
+procedureMemoryLimit : PROCEDURE memoryLimit ;
+
+procedureResult : ( variable AS variable ) | variable ;
+
+returnBody : returnItems ( order )? ( skip )? ( limit )? ;
+
+returnItems : ( '*' ( ',' returnItem )* )
+            | ( returnItem ( ',' returnItem )* )
+            ;
+
+returnItem : ( expression AS variable )
+           | expression
+           ;
+
+order : ORDER BY sortItem ( ',' sortItem )* ;
+
+skip : L_SKIP expression ;
+
+limit : LIMIT expression ;
+
+sortItem : expression ( ASCENDING | ASC | DESCENDING | DESC )? ;
+
+where : WHERE expression ;
+
+pattern : patternPart ( ',' patternPart )* ;
+
+patternPart : ( variable '=' anonymousPatternPart )
+            | anonymousPatternPart
+            ;
+
+anonymousPatternPart : patternElement ;
+
+patternElement : ( nodePattern ( patternElementChain )* )
+               | ( '(' patternElement ')' )
+               ;
+
+nodePattern : '(' ( variable )? ( nodeLabels )? ( properties )? ')' ;
+
+patternElementChain : relationshipPattern nodePattern ;
+
+relationshipPattern : ( leftArrowHead dash ( relationshipDetail )? dash rightArrowHead )
+                    | ( leftArrowHead dash ( relationshipDetail )? dash )
+                    | ( dash ( relationshipDetail )? dash rightArrowHead )
+                    | ( dash ( relationshipDetail )? dash )
+                    ;
+
+leftArrowHead : '<' | LeftArrowHeadPart ;
+rightArrowHead : '>' | RightArrowHeadPart ;
+dash : '-' | DashPart ;
+
+relationshipDetail : '[' ( name=variable )? ( relationshipTypes )? ( variableExpansion )?  properties ']'
+                   | '[' ( name=variable )? ( relationshipTypes )? ( variableExpansion )? relationshipLambda ( total_weight=variable )? (relationshipLambda )? ']'
+                   | '[' ( name=variable )? ( relationshipTypes )? ( variableExpansion )? (properties )* ( relationshipLambda total_weight=variable )? (relationshipLambda )? ']';
+
+relationshipLambda: '(' traversed_edge=variable ',' traversed_node=variable '|' expression ')';
+
+variableExpansion : '*' (BFS | WSHORTEST)? ( expression )? ( '..' ( expression )? )? ;
+
+properties : mapLiteral
+           | parameter
+           ;
+
+relationshipTypes : ':' relTypeName ( '|' ':'? relTypeName )* ;
+
+nodeLabels : nodeLabel ( nodeLabel )* ;
+
+nodeLabel : ':' labelName ;
+
+labelName : symbolicName ;
+
+relTypeName : symbolicName ;
+
+expression : expression12 ;
+
+expression12 : expression11 ( OR expression11 )* ;
+
+expression11 : expression10 ( XOR expression10 )* ;
+
+expression10 : expression9 ( AND expression9 )* ;
+
+expression9 : ( NOT )* expression8 ;
+
+expression8 : expression7 ( partialComparisonExpression )* ;
+
+expression7 : expression6 ( ( '+' expression6 ) | ( '-' expression6 ) )* ;
+
+expression6 : expression5 ( ( '*' expression5 ) | ( '/' expression5 ) | ( '%' expression5 ) )* ;
+
+expression5 : expression4 ( '^' expression4 )* ;
+
+expression4 : ( ( '+' | '-' ) )* expression3a ;
+
+expression3a : expression3b ( stringAndNullOperators )* ;
+
+stringAndNullOperators : ( ( ( ( '=~' ) | ( IN ) | ( STARTS WITH ) | ( ENDS WITH ) | ( CONTAINS ) ) expression3b) | ( IS CYPHERNULL ) | ( IS NOT CYPHERNULL ) ) ;
+
+expression3b : expression2a ( listIndexingOrSlicing )* ;
+
+listIndexingOrSlicing : ( '[' expression ']' )
+                      | ( '[' lower_bound=expression? '..' upper_bound=expression? ']' )
+                      ;
+
+expression2a : expression2b ( nodeLabels )? ;
+
+expression2b : atom ( propertyLookup )* ;
+
+atom : literal
+     | parameter
+     | caseExpression
+     | ( COUNT '(' '*' ')' )
+     | listComprehension
+     | patternComprehension
+     | ( FILTER '(' filterExpression ')' )
+     | ( EXTRACT '(' extractExpression ')' )
+     | ( REDUCE '(' reduceExpression ')' )
+     | ( COALESCE '(' expression ( ',' expression )* ')' )
+     | ( ALL '(' filterExpression ')' )
+     | ( ANY '(' filterExpression ')' )
+     | ( NONE '(' filterExpression ')' )
+     | ( SINGLE '(' filterExpression ')' )
+     | relationshipsPattern
+     | parenthesizedExpression
+     | functionInvocation
+     | variable
+     ;
+
+literal : numberLiteral
+        | StringLiteral
+        | booleanLiteral
+        | CYPHERNULL
+        | mapLiteral
+        | listLiteral
+        ;
+
+booleanLiteral : TRUE
+               | FALSE
+               ;
+
+listLiteral : '[' ( expression ( ',' expression )* )? ']' ;
+
+partialComparisonExpression : ( '=' expression7 )
+                            | ( '<>' expression7 )
+                            | ( '!=' expression7 )
+                            | ( '<' expression7 )
+                            | ( '>' expression7 )
+                            | ( '<=' expression7 )
+                            | ( '>=' expression7 )
+                            ;
+
+parenthesizedExpression : '(' expression ')' ;
+
+relationshipsPattern : nodePattern ( patternElementChain )+ ;
+
+filterExpression : idInColl ( where )? ;
+
+reduceExpression : accumulator=variable '=' initial=expression ',' idInColl '|' expression ;
+
+extractExpression : idInColl '|' expression ;
+
+idInColl : variable IN expression ;
+
+functionInvocation : functionName '(' ( DISTINCT )? ( expression ( ',' expression )* )? ')' ;
+
+functionName : symbolicName ( '.' symbolicName )* ;
+
+listComprehension : '[' filterExpression ( '|' expression )? ']' ;
+
+patternComprehension : '[' ( variable '=' )? relationshipsPattern ( WHERE expression )? '|' expression ']' ;
+
+propertyLookup : '.' ( propertyKeyName ) ;
+
+caseExpression : ( ( CASE ( caseAlternatives )+ ) | ( CASE test=expression ( caseAlternatives )+ ) ) ( ELSE else_expression=expression )? END ;
+
+caseAlternatives : WHEN when_expression=expression THEN then_expression=expression ;
+
+variable : symbolicName ;
+
+numberLiteral : doubleLiteral
+              | integerLiteral
+              ;
+
+mapLiteral : '{' ( propertyKeyName ':' expression ( ',' propertyKeyName ':' expression )* )? '}' ;
+
+parameter : '$' ( symbolicName | DecimalLiteral ) ;
+
+propertyExpression : atom ( propertyLookup )+ ;
+
+propertyKeyName : symbolicName ;
+
+integerLiteral : DecimalLiteral
+               | OctalLiteral
+               | HexadecimalLiteral
+               ;
+
+createIndex : CREATE INDEX ON ':' labelName ( '(' propertyKeyName ')' )? ;
+
+dropIndex : DROP INDEX ON ':' labelName ( '(' propertyKeyName ')' )? ;
+
+doubleLiteral : FloatingLiteral ;
+
+cypherKeyword : ALL
+              | AND
+              | ANY
+              | AS
+              | ASC
+              | ASCENDING
+              | ASSERT
+              | BFS
+              | BY
+              | CALL
+              | CASE
+              | CONSTRAINT
+              | CONTAINS
+              | COUNT
+              | CREATE
+              | CYPHERNULL
+              | DELETE
+              | DESC
+              | DESCENDING
+              | DETACH
+              | DISTINCT
+              | ELSE
+              | END
+              | ENDS
+              | EXISTS
+              | EXPLAIN
+              | EXTRACT
+              | FALSE
+              | FILTER
+              | IN
+              | INDEX
+              | INFO
+              | IS
+              | KEY
+              | LIMIT
+              | L_SKIP
+              | MATCH
+              | MERGE
+              | NODE
+              | NONE
+              | NOT
+              | ON
+              | OPTIONAL
+              | OR
+              | ORDER
+              | PROCEDURE
+              | PROFILE
+              | QUERY
+              | REDUCE
+              | REMOVE
+              | RETURN
+              | SET
+              | SHOW
+              | SINGLE
+              | STARTS
+              | STORAGE
+              | THEN
+              | TRUE
+              | UNION
+              | UNIQUE
+              | UNWIND
+              | WHEN
+              | WHERE
+              | WITH
+              | WSHORTEST
+              | XOR
+              | YIELD
+              ;
+
+symbolicName : UnescapedSymbolicName
+             | EscapedSymbolicName
+             | cypherKeyword
+             ;

src/parser/opencypher/grammar/CypherLexer.g4

@@ -0,0 +1,208 @@
+/*
+ * When changing this grammar make sure to update constants in
+ * src/parser/stripped_lexer_constants.hpp (kKeywords, kSpecialTokens
+ * and bitsets) if needed.
+ */
+
+lexer grammar CypherLexer ;
+
+import UnicodeCategories ;
+
+/* Skip whitespace and comments. */
+Skipped              : ( Whitespace | Comment ) -> skip ;
+
+fragment Whitespace  : '\u0020'
+                     | [\u0009-\u000D]
+                     | [\u001C-\u001F]
+                     | '\u1680' | '\u180E'
+                     | [\u2000-\u200A]
+                     | '\u2028' | '\u2029'
+                     | '\u205F'
+                     | '\u3000'
+                     | '\u00A0'
+                     | '\u202F'
+                     ;
+
+fragment Comment     : '/*' .*? '*/'
+                     | '//' ~[\r\n]*
+                     ;
+
+/* Special symbols. */
+LPAREN    : '(' ;
+RPAREN    : ')' ;
+LBRACK    : '[' ;
+RBRACK    : ']' ;
+LBRACE    : '{' ;
+RBRACE    : '}' ;
+
+COMMA     : ',' ;
+DOT       : '.' ;
+DOTS      : '..' ;
+COLON     : ':' ;
+SEMICOLON : ';' ;
+DOLLAR    : '$' ;
+PIPE      : '|' ;
+
+EQ        : '=' ;
+LT        : '<' ;
+GT        : '>' ;
+LTE       : '<=' ;
+GTE       : '>=' ;
+NEQ1      : '<>' ;
+NEQ2      : '!=' ;
+SIM       : '=~' ;
+
+PLUS      : '+' ;
+MINUS     : '-' ;
+ASTERISK  : '*' ;
+SLASH     : '/' ;
+PERCENT   : '%' ;
+CARET     : '^' ;
+PLUS_EQ   : '+=' ;
+
+/* Some random unicode characters that can be used to draw arrows. */
+LeftArrowHeadPart  : '⟨' | '〈' | '﹤' | '＜' ;
+RightArrowHeadPart : '⟩' | '〉' | '﹥' | '＞' ;
+DashPart           : '­' | '‐' | '‑' | '‒' | '–' | '—' | '―'
+                   | '−' | '﹘' | '﹣' | '－'
+                   ;
+
+/* Cypher reserved words. */
+ALL            : A L L ;
+AND            : A N D ;
+ANY            : A N Y ;
+AS             : A S ;
+ASC            : A S C ;
+ASCENDING      : A S C E N D I N G ;
+ASSERT         : A S S E R T ;
+BFS            : B F S ;
+BY             : B Y ;
+CALL           : C A L L ;
+CASE           : C A S E ;
+COALESCE       : C O A L E S C E ;
+CONSTRAINT     : C O N S T R A I N T ;
+CONTAINS       : C O N T A I N S ;
+COUNT          : C O U N T ;
+CREATE         : C R E A T E ;
+CYPHERNULL     : N U L L ;
+DELETE         : D E L E T E ;
+DESC           : D E S C ;
+DESCENDING     : D E S C E N D I N G ;
+DETACH         : D E T A C H ;
+DISTINCT       : D I S T I N C T ;
+DROP           : D R O P ;
+ELSE           : E L S E ;
+END            : E N D ;
+ENDS           : E N D S ;
+EXISTS         : E X I S T S ;
+EXPLAIN        : E X P L A I N ;
+EXTRACT        : E X T R A C T ;
+FALSE          : F A L S E ;
+FILTER         : F I L T E R ;
+IN             : I N ;
+INDEX          : I N D E X ;
+INFO           : I N F O ;
+IS             : I S ;
+KB             : K B ;
+KEY            : K E Y ;
+LIMIT          : L I M I T ;
+L_SKIP         : S K I P ;
+MATCH          : M A T C H ;
+MB             : M B ;
+MEMORY         : M E M O R Y ;
+MERGE          : M E R G E ;
+NODE           : N O D E ;
+NONE           : N O N E ;
+NOT            : N O T ;
+ON             : O N ;
+OPTIONAL       : O P T I O N A L ;
+OR             : O R ;
+ORDER          : O R D E R ;
+PROCEDURE      : P R O C E D U R E ;
+PROFILE        : P R O F I L E ;
+QUERY          : Q U E R Y ;
+REDUCE         : R E D U C E ;
+REMOVE         : R E M O V E ;
+RETURN         : R E T U R N ;
+SET            : S E T ;
+SHOW           : S H O W ;
+SINGLE         : S I N G L E ;
+STARTS         : S T A R T S ;
+STORAGE        : S T O R A G E ;
+THEN           : T H E N ;
+TRUE           : T R U E ;
+UNION          : U N I O N ;
+UNIQUE         : U N I Q U E ;
+UNLIMITED      : U N L I M I T E D ;
+UNWIND         : U N W I N D ;
+WHEN           : W H E N ;
+WHERE          : W H E R E ;
+WITH           : W I T H ;
+WSHORTEST      : W S H O R T E S T ;
+XOR            : X O R ;
+YIELD          : Y I E L D ;
+
+/* Double and single quoted string literals. */
+StringLiteral : '"'  ( ~[\\"] | EscapeSequence )* '"'
+              | '\'' ( ~[\\'] | EscapeSequence )* '\''
+              ;
+
+fragment EscapeSequence : '\\' ( B | F | N | R | T | '\\' | '\'' | '"' )
+                        | '\\u' HexDigit HexDigit HexDigit HexDigit
+                        | '\\U' HexDigit HexDigit HexDigit HexDigit
+                                HexDigit HexDigit HexDigit HexDigit
+                        ;
+
+/* Number literals. */
+DecimalLiteral     : '0' | NonZeroDigit ( DecDigit )* ;
+OctalLiteral       : '0' ( OctDigit )+ ;
+HexadecimalLiteral : '0x' ( HexDigit )+ ;
+FloatingLiteral    : DecDigit* '.' DecDigit+ ( E '-'? DecDigit+ )?
+                   | DecDigit+ ( '.' DecDigit* )? ( E '-'? DecDigit+ )
+                   | DecDigit+ ( E '-'? DecDigit+ )
+                   ;
+
+fragment NonZeroDigit : [1-9] ;
+fragment DecDigit     : [0-9] ;
+fragment OctDigit     : [0-7] ;
+fragment HexDigit     : [0-9] | [a-f] | [A-F] ;
+
+/* Symbolic names. */
+UnescapedSymbolicName : IdentifierStart ( IdentifierPart )* ;
+EscapedSymbolicName   : ( '`' ~[`]* '`' )+ ;
+
+/**
+ * Based on the unicode identifier and pattern syntax
+ * (http://www.unicode.org/reports/tr31/)
+ * and extended with a few characters.
+ */
+IdentifierStart : ID_Start    | Pc ;
+IdentifierPart  : ID_Continue | Sc ;
+
+/* Hack for case-insensitive reserved words */
+fragment A : 'A' | 'a' ;
+fragment B : 'B' | 'b' ;
+fragment C : 'C' | 'c' ;
+fragment D : 'D' | 'd' ;
+fragment E : 'E' | 'e' ;
+fragment F : 'F' | 'f' ;
+fragment G : 'G' | 'g' ;
+fragment H : 'H' | 'h' ;
+fragment I : 'I' | 'i' ;
+fragment J : 'J' | 'j' ;
+fragment K : 'K' | 'k' ;
+fragment L : 'L' | 'l' ;
+fragment M : 'M' | 'm' ;
+fragment N : 'N' | 'n' ;
+fragment O : 'O' | 'o' ;
+fragment P : 'P' | 'p' ;
+fragment Q : 'Q' | 'q' ;
+fragment R : 'R' | 'r' ;
+fragment S : 'S' | 's' ;
+fragment T : 'T' | 't' ;
+fragment U : 'U' | 'u' ;
+fragment V : 'V' | 'v' ;
+fragment W : 'W' | 'w' ;
+fragment X : 'X' | 'x' ;
+fragment Y : 'Y' | 'y' ;
+fragment Z : 'Z' | 'z' ;

src/parser/opencypher/grammar/MemgraphCypher.g4

@@ -0,0 +1,399 @@
+/*
+ * Copyright 2021 Memgraph Ltd.
+ *
+ * Use of this software is governed by the Business Source License
+ * included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+ * License, and you may not use this file except in compliance with the Business Source License.
+ *
+ * As of the Change Date specified in that file, in accordance with
+ * the Business Source License, use of this software will be governed
+ * by the Apache License, Version 2.0, included in the file
+ * licenses/APL.txt.
+ */
+
+/* Memgraph specific part of Cypher grammar with enterprise features. */
+
+parser grammar MemgraphCypher ;
+
+options { tokenVocab=MemgraphCypherLexer; }
+
+import Cypher ;
+
+memgraphCypherKeyword : cypherKeyword
+                      | AFTER
+                      | ALTER
+                      | ASYNC
+                      | AUTH
+                      | BAD
+                      | BATCH_INTERVAL
+                      | BATCH_LIMIT
+                      | BATCH_SIZE
+                      | BEFORE
+                      | BOOTSTRAP_SERVERS
+                      | CHECK
+                      | CLEAR
+                      | COMMIT
+                      | COMMITTED
+                      | CONFIG
+                      | CONFIGS
+                      | CONSUMER_GROUP
+                      | CREDENTIALS
+                      | CSV
+                      | DATA
+                      | DELIMITER
+                      | DATABASE
+                      | DENY
+                      | DROP
+                      | DUMP
+                      | EXECUTE
+                      | FREE
+                      | FROM
+                      | FOR
+                      | FOREACH
+                      | GLOBAL
+                      | GRANT
+                      | HEADER
+                      | IDENTIFIED
+                      | ISOLATION
+                      | KAFKA
+                      | LEVEL
+                      | LOAD
+                      | LOCK
+                      | MAIN
+                      | MODE
+                      | NEXT
+                      | NO
+                      | PASSWORD
+                      | PULSAR
+                      | PORT
+                      | PRIVILEGES
+                      | READ
+                      | REGISTER
+                      | REPLICA
+                      | REPLICAS
+                      | REPLICATION
+                      | REVOKE
+                      | ROLE
+                      | ROLES
+                      | QUOTE
+                      | SCHEMA
+                      | SCHEMAS
+                      | SESSION
+                      | SETTING
+                      | SETTINGS
+                      | SNAPSHOT
+                      | START
+                      | STATS
+                      | STREAM
+                      | STREAMS
+                      | SYNC
+                      | TIMEOUT
+                      | TO
+                      | TOPICS
+                      | TRANSACTION
+                      | TRANSFORM
+                      | TRIGGER
+                      | TRIGGERS
+                      | UNCOMMITTED
+                      | UNLOCK
+                      | UPDATE
+                      | USER
+                      | USERS
+                      | VERSION
+                      ;
+
+symbolicName : UnescapedSymbolicName
+             | EscapedSymbolicName
+             | memgraphCypherKeyword
+             ;
+
+query : cypherQuery
+      | indexQuery
+      | explainQuery
+      | profileQuery
+      | infoQuery
+      | constraintQuery
+      | authQuery
+      | dumpQuery
+      | replicationQuery
+      | lockPathQuery
+      | freeMemoryQuery
+      | triggerQuery
+      | isolationLevelQuery
+      | createSnapshotQuery
+      | streamQuery
+      | settingQuery
+      | versionQuery
+      | schemaQuery
+      ;
+
+authQuery : createRole
+          | dropRole
+          | showRoles
+          | createUser
+          | setPassword
+          | dropUser
+          | showUsers
+          | setRole
+          | clearRole
+          | grantPrivilege
+          | denyPrivilege
+          | revokePrivilege
+          | showPrivileges
+          | showRoleForUser
+          | showUsersForRole
+          ;
+
+replicationQuery : setReplicationRole
+                 | showReplicationRole
+                 | registerReplica
+                 | dropReplica
+                 | showReplicas
+                 ;
+
+triggerQuery : createTrigger
+             | dropTrigger
+             | showTriggers
+             ;
+
+clause : cypherMatch
+       | unwind
+       | merge
+       | create
+       | set
+       | cypherDelete
+       | remove
+       | with
+       | cypherReturn
+       | callProcedure
+       | loadCsv
+       | foreach
+       ;
+
+updateClause : set
+             | remove
+             | create
+             | merge
+             | cypherDelete
+             | foreach
+             ;
+
+foreach :  FOREACH '(' variable IN expression '|' updateClause+  ')' ;
+
+streamQuery : checkStream
+            | createStream
+            | dropStream
+            | startStream
+            | startAllStreams
+            | stopStream
+            | stopAllStreams
+            | showStreams
+            ;
+
+settingQuery : setSetting
+             | showSetting
+             | showSettings
+             ;
+
+schemaQuery : showSchema
+            | showSchemas
+            | createSchema
+            | dropSchema
+            ;
+
+loadCsv : LOAD CSV FROM csvFile ( WITH | NO ) HEADER
+         ( IGNORE BAD ) ?
+         ( DELIMITER delimiter ) ?
+         ( QUOTE quote ) ?
+         AS rowVar ;
+
+csvFile : literal ;
+
+delimiter : literal ;
+
+quote : literal ;
+
+rowVar : variable ;
+
+userOrRoleName : symbolicName ;
+
+createRole : CREATE ROLE role=userOrRoleName ;
+
+dropRole   : DROP ROLE role=userOrRoleName ;
+
+showRoles  : SHOW ROLES ;
+
+createUser : CREATE USER user=userOrRoleName
+             ( IDENTIFIED BY password=literal )? ;
+
+setPassword : SET PASSWORD FOR user=userOrRoleName TO password=literal;
+
+dropUser : DROP USER user=userOrRoleName ;
+
+showUsers : SHOW USERS ;
+
+setRole : SET ROLE FOR user=userOrRoleName TO role=userOrRoleName;
+
+clearRole : CLEAR ROLE FOR user=userOrRoleName ;
+
+grantPrivilege : GRANT ( ALL PRIVILEGES | privileges=privilegeList ) TO userOrRole=userOrRoleName ;
+
+denyPrivilege : DENY ( ALL PRIVILEGES | privileges=privilegeList ) TO userOrRole=userOrRoleName ;
+
+revokePrivilege : REVOKE ( ALL PRIVILEGES | privileges=privilegeList ) FROM userOrRole=userOrRoleName ;
+
+privilege : CREATE
+          | DELETE
+          | MATCH
+          | MERGE
+          | SET
+          | REMOVE
+          | INDEX
+          | STATS
+          | AUTH
+          | CONSTRAINT
+          | DUMP
+          | REPLICATION
+          | READ_FILE
+          | FREE_MEMORY
+          | TRIGGER
+          | CONFIG
+          | DURABILITY
+          | STREAM
+          | MODULE_READ
+          | MODULE_WRITE
+          | WEBSOCKET
+          | SCHEMA
+          ;
+
+privilegeList : privilege ( ',' privilege )* ;
+
+showPrivileges : SHOW PRIVILEGES FOR userOrRole=userOrRoleName ;
+
+showRoleForUser : SHOW ROLE FOR user=userOrRoleName ;
+
+showUsersForRole : SHOW USERS FOR role=userOrRoleName ;
+
+dumpQuery: DUMP DATABASE ;
+
+setReplicationRole  : SET REPLICATION ROLE TO ( MAIN | REPLICA )
+                      ( WITH PORT port=literal ) ? ;
+
+showReplicationRole : SHOW REPLICATION ROLE ;
+
+replicaName : symbolicName ;
+
+socketAddress : literal ;
+
+registerReplica : REGISTER REPLICA replicaName ( SYNC | ASYNC )
+                TO socketAddress ;
+
+dropReplica : DROP REPLICA replicaName ;
+
+showReplicas  : SHOW REPLICAS ;
+
+lockPathQuery : ( LOCK | UNLOCK ) DATA DIRECTORY ;
+
+freeMemoryQuery : FREE MEMORY ;
+
+triggerName : symbolicName ;
+
+triggerStatement : .*? ;
+
+emptyVertex : '(' ')' ;
+
+emptyEdge : dash dash rightArrowHead ;
+
+createTrigger : CREATE TRIGGER triggerName ( ON ( emptyVertex | emptyEdge ) ? ( CREATE | UPDATE | DELETE ) ) ?
+              ( AFTER | BEFORE ) COMMIT EXECUTE triggerStatement ;
+
+dropTrigger : DROP TRIGGER triggerName ;
+
+showTriggers : SHOW TRIGGERS ;
+
+isolationLevel : SNAPSHOT ISOLATION | READ COMMITTED | READ UNCOMMITTED ;
+
+isolationLevelScope : GLOBAL | SESSION | NEXT ;
+
+isolationLevelQuery : SET isolationLevelScope TRANSACTION ISOLATION LEVEL isolationLevel ;
+
+createSnapshotQuery : CREATE SNAPSHOT ;
+
+streamName : symbolicName ;
+
+symbolicNameWithMinus : symbolicName ( MINUS symbolicName )* ;
+
+symbolicNameWithDotsAndMinus: symbolicNameWithMinus ( DOT symbolicNameWithMinus )* ;
+
+symbolicTopicNames : symbolicNameWithDotsAndMinus ( COMMA symbolicNameWithDotsAndMinus )* ;
+
+topicNames : symbolicTopicNames | literal ;
+
+commonCreateStreamConfig : TRANSFORM transformationName=procedureName
+                         | BATCH_INTERVAL batchInterval=literal
+                         | BATCH_SIZE batchSize=literal
+                         ;
+
+createStream : kafkaCreateStream | pulsarCreateStream ;
+
+configKeyValuePair : literal ':' literal ;
+
+configMap : '{' ( configKeyValuePair ( ',' configKeyValuePair )* )? '}' ;
+
+kafkaCreateStreamConfig : TOPICS topicNames
+                        | CONSUMER_GROUP consumerGroup=symbolicNameWithDotsAndMinus
+                        | BOOTSTRAP_SERVERS bootstrapServers=literal
+                        | CONFIGS configsMap=configMap
+                        | CREDENTIALS credentialsMap=configMap
+                        | commonCreateStreamConfig
+                        ;
+
+kafkaCreateStream : CREATE KAFKA STREAM streamName ( kafkaCreateStreamConfig ) * ;
+
+
+pulsarCreateStreamConfig : TOPICS topicNames
+                         | SERVICE_URL serviceUrl=literal
+                         | commonCreateStreamConfig
+                         ;
+
+pulsarCreateStream : CREATE PULSAR STREAM streamName ( pulsarCreateStreamConfig ) * ;
+
+dropStream : DROP STREAM streamName ;
+
+startStream : START STREAM streamName ( BATCH_LIMIT batchLimit=literal ) ? ( TIMEOUT timeout=literal ) ? ;
+
+startAllStreams : START ALL STREAMS ;
+
+stopStream : STOP STREAM streamName ;
+
+stopAllStreams : STOP ALL STREAMS ;
+
+showStreams : SHOW STREAMS ;
+
+checkStream : CHECK STREAM streamName ( BATCH_LIMIT batchLimit=literal ) ? ( TIMEOUT timeout=literal ) ? ;
+
+settingName : literal ;
+
+settingValue : literal ;
+
+setSetting : SET DATABASE SETTING settingName TO settingValue ;
+
+showSetting : SHOW DATABASE SETTING settingName ;
+
+showSettings : SHOW DATABASE SETTINGS ;
+
+versionQuery : SHOW VERSION ;
+
+showSchema : SHOW SCHEMA ON ':' labelName ;
+
+showSchemas : SHOW SCHEMAS ;
+
+propertyType : symbolicName ;
+
+propertyKeyTypePair : propertyKeyName propertyType ;
+
+schemaPropertyMap : '(' propertyKeyTypePair ( ',' propertyKeyTypePair )* ')' ;
+
+createSchema : CREATE SCHEMA ON ':' labelName schemaPropertyMap ;
+
+dropSchema : DROP SCHEMA ON ':' labelName ;

src/parser/opencypher/grammar/MemgraphCypherLexer.g4

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2021 Memgraph Ltd.
+ *
+ * Use of this software is governed by the Business Source License
+ * included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+ * License, and you may not use this file except in compliance with the Business Source License.
+ *
+ * As of the Change Date specified in that file, in accordance with
+ * the Business Source License, use of this software will be governed
+ * by the Apache License, Version 2.0, included in the file
+ * licenses/APL.txt.
+ */
+
+/* Memgraph specific Cypher reserved words used for enterprise features. */
+
+/*
+ * When changing this grammar make sure to update constants in
+ * src/parser/stripped_lexer_constants.hpp (kKeywords, kSpecialTokens
+ * and bitsets) if needed.
+ */
+
+lexer grammar MemgraphCypherLexer ;
+
+import CypherLexer ;
+
+UNDERSCORE : '_' ;
+
+AFTER               : A F T E R ;
+ALTER               : A L T E R ;
+ASYNC               : A S Y N C ;
+AUTH                : A U T H ;
+BAD                 : B A D ;
+BATCH_INTERVAL      : B A T C H UNDERSCORE I N T E R V A L ;
+BATCH_LIMIT         : B A T C H UNDERSCORE L I M I T ;
+BATCH_SIZE          : B A T C H UNDERSCORE S I Z E ;
+BEFORE              : B E F O R E ;
+BOOTSTRAP_SERVERS   : B O O T S T R A P UNDERSCORE S E R V E R S ;
+CHECK               : C H E C K ;
+CLEAR               : C L E A R ;
+COMMIT              : C O M M I T ;
+COMMITTED           : C O M M I T T E D ;
+CONFIG              : C O N F I G ;
+CONFIGS             : C O N F I G S;
+CONSUMER_GROUP      : C O N S U M E R UNDERSCORE G R O U P ;
+CREDENTIALS         : C R E D E N T I A L S ;
+CSV                 : C S V ;
+DATA                : D A T A ;
+DELIMITER           : D E L I M I T E R ;
+DATABASE            : D A T A B A S E ;
+DENY                : D E N Y ;
+DIRECTORY           : D I R E C T O R Y ;
+DROP                : D R O P ;
+DUMP                : D U M P ;
+DURABILITY          : D U R A B I L I T Y ;
+EXECUTE             : E X E C U T E ;
+FOR                 : F O R ;
+FOREACH             : F O R E A C H;
+FREE                : F R E E ;
+FREE_MEMORY         : F R E E UNDERSCORE M E M O R Y ;
+FROM                : F R O M ;
+GLOBAL              : G L O B A L ;
+GRANT               : G R A N T ;
+GRANTS              : G R A N T S ;
+HEADER              : H E A D E R ;
+IDENTIFIED          : I D E N T I F I E D ;
+IGNORE              : I G N O R E ;
+ISOLATION           : I S O L A T I O N ;
+KAFKA               : K A F K A ;
+LEVEL               : L E V E L ;
+LOAD                : L O A D ;
+LOCK                : L O C K ;
+MAIN                : M A I N ;
+MODE                : M O D E ;
+MODULE_READ         : M O D U L E UNDERSCORE R E A D ;
+MODULE_WRITE        : M O D U L E UNDERSCORE W R I T E ;
+NEXT                : N E X T ;
+NO                  : N O ;
+PASSWORD            : P A S S W O R D ;
+PORT                : P O R T ;
+PRIVILEGES          : P R I V I L E G E S ;
+PULSAR              : P U L S A R ;
+READ                : R E A D ;
+READ_FILE           : R E A D UNDERSCORE F I L E ;
+REGISTER            : R E G I S T E R ;
+REPLICA             : R E P L I C A ;
+REPLICAS            : R E P L I C A S ;
+REPLICATION         : R E P L I C A T I O N ;
+REVOKE              : R E V O K E ;
+ROLE                : R O L E ;
+ROLES               : R O L E S ;
+QUOTE               : Q U O T E ;
+SCHEMA              : S C H E M A ;
+SCHEMAS             : S C H E M A S ;
+SERVICE_URL         : S E R V I C E UNDERSCORE U R L ;
+SESSION             : S E S S I O N ;
+SETTING             : S E T T I N G ;
+SETTINGS            : S E T T I N G S ;
+SNAPSHOT            : S N A P S H O T ;
+START               : S T A R T ;
+STATS               : S T A T S ;
+STOP                : S T O P ;
+STREAM              : S T R E A M ;
+STREAMS             : S T R E A M S ;
+SYNC                : S Y N C ;
+TIMEOUT             : T I M E O U T ;
+TO                  : T O ;
+TOPICS              : T O P I C S;
+TRANSACTION         : T R A N S A C T I O N ;
+TRANSFORM           : T R A N S F O R M ;
+TRIGGER             : T R I G G E R ;
+TRIGGERS            : T R I G G E R S ;
+UNCOMMITTED         : U N C O M M I T T E D ;
+UNLOCK              : U N L O C K ;
+UPDATE              : U P D A T E ;
+USER                : U S E R ;
+USERS               : U S E R S ;
+VERSION             : V E R S I O N ;
+WEBSOCKET           : W E B S O C K E T ;

src/parser/opencypher/parser.hpp

@@ -0,0 +1,85 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <string>
+
+#include "antlr4-runtime.h"
+#include "utils/exceptions.hpp"
+#include "parser/opencypher/generated/MemgraphCypher.h"
+#include "parser/opencypher/generated/MemgraphCypherLexer.h"
+#include "utils/concepts.hpp"
+
+namespace memgraph::frontend::opencypher {
+
+class SyntaxException : public utils::BasicException {
+ public:
+  using utils::BasicException::BasicException;
+  SyntaxException() : SyntaxException("") {}
+};
+
+/**
+ * Generates openCypher AST
+ * This thing must me a class since parser.cypher() returns pointer and there is
+ * no way for us to get ownership over the object.
+ */
+enum class ParserOpTag : uint8_t {
+  CYPHER, EXPRESSION
+};
+
+template<ParserOpTag Tag = ParserOpTag::CYPHER>
+class Parser {
+ public:
+  /**
+   * @param query incoming query that has to be compiled into query plan
+   *        the first step is to generate AST
+   */
+  Parser(const std::string query) : query_(std::move(query)) {
+    parser_.removeErrorListeners();
+    parser_.addErrorListener(&error_listener_);
+    if constexpr(Tag == ParserOpTag::CYPHER) {
+      tree_ = parser_.cypher();
+    }
+    else {
+      tree_ = parser_.expression();
+    }
+    if (parser_.getNumberOfSyntaxErrors()) {
+      throw SyntaxException(error_listener_.error_);
+    }
+  }
+
+  auto tree() { return tree_; }
+
+ private:
+  class FirstMessageErrorListener : public antlr4::BaseErrorListener {
+    void syntaxError(antlr4::Recognizer *, antlr4::Token *, size_t line, size_t position, const std::string &message,
+                     std::exception_ptr) override {
+      if (error_.empty()) {
+        error_ = "line " + std::to_string(line) + ":" + std::to_string(position + 1) + " " + message;
+      }
+    }
+
+   public:
+    std::string error_;
+  };
+
+  FirstMessageErrorListener error_listener_;
+  std::string query_;
+  antlr4::ANTLRInputStream input_{query_};
+  antlropencypher::MemgraphCypherLexer lexer_{&input_};
+  antlr4::CommonTokenStream tokens_{&lexer_};
+
+  // generate ast
+  antlropencypher::MemgraphCypher parser_{&tokens_};
+  antlr4::tree::ParseTree *tree_ = nullptr;
+};
+}  // namespace memgraph::frontend::opencypher

src/query/cypher_query_interpreter.cpp

@@ -12,7 +12,7 @@
 #include "query/cypher_query_interpreter.hpp"
 
 // NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_bool(query_cost_planner, true, "Use the cost-estimating query planner.");
+DEFINE_HIDDEN_bool(query_cost_planner, true, "Use the cost-estimating query planner.");
 // NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
 DEFINE_VALIDATED_int32(query_plan_cache_ttl, 60, "Time to live for cached query plans, in seconds.",
                        FLAG_IN_RANGE(0, std::numeric_limits<int32_t>::max()));

src/query/db_accessor.hpp

@@ -51,7 +51,6 @@ class EdgeAccessor final {
  public:
   storage::EdgeAccessor impl_;
 
- public:
   explicit EdgeAccessor(storage::EdgeAccessor impl) : impl_(std::move(impl)) {}
 
   bool IsVisible(storage::View view) const { return impl_.IsVisible(view); }
@@ -97,7 +96,6 @@ class VertexAccessor final {
 
   static EdgeAccessor MakeEdgeAccessor(const storage::EdgeAccessor impl) { return EdgeAccessor(impl); }
 
- public:
   explicit VertexAccessor(storage::VertexAccessor impl) : impl_(impl) {}
 
   bool IsVisible(storage::View view) const { return impl_.IsVisible(view); }
@@ -324,7 +322,7 @@ class DbAccessor final {
 
   void AdvanceCommand() { accessor_->AdvanceCommand(); }
 
-  utils::BasicResult<storage::StorageDataManipulationError, void> Commit() { return accessor_->Commit(); }
+  utils::BasicResult<storage::ConstraintViolation, void> Commit() { return accessor_->Commit(); }
 
   void Abort() { accessor_->Abort(); }
 

src/query/exceptions.hpp

@@ -188,12 +188,6 @@ class FreeMemoryModificationInMulticommandTxException : public QueryException {
       : QueryException("Free memory query not allowed in multicommand transactions.") {}
 };
 
-class ShowConfigModificationInMulticommandTxException : public QueryException {
- public:
-  ShowConfigModificationInMulticommandTxException()
-      : QueryException("Show config query not allowed in multicommand transactions.") {}
-};
-
 class TriggerModificationInMulticommandTxException : public QueryException {
  public:
   TriggerModificationInMulticommandTxException()
@@ -230,11 +224,4 @@ class VersionInfoInMulticommandTxException : public QueryException {
       : QueryException("Version info query not allowed in multicommand transactions.") {}
 };
 
-class ReplicationException : public utils::BasicException {
- public:
-  using utils::BasicException::BasicException;
-  explicit ReplicationException(const std::string &message)
-      : utils::BasicException("Replication Exception: {} Check the status of the replicas using 'SHOW REPLICA' query.",
-                              message) {}
-};
 }  // namespace memgraph::query

src/query/frontend/ast/ast.lcp

@@ -2665,13 +2665,5 @@ cpp<#
   (:serialize (:slk))
   (:clone))
 
-  (lcp:define-class show-config-query (query) ()
-  (:public
-    #>cpp
-    DEFVISITABLE(QueryVisitor<void>);
-    cpp<#)
-  (:serialize (:slk))
-  (:clone))
-
 (lcp:pop-namespace) ;; namespace query
 (lcp:pop-namespace) ;; namespace memgraph

src/query/frontend/ast/ast_visitor.hpp

@@ -94,7 +94,6 @@ class StreamQuery;
 class SettingQuery;
 class VersionQuery;
 class Foreach;
-class ShowConfigQuery;
 
 using TreeCompositeVisitor = utils::CompositeVisitor<
     SingleQuery, CypherUnion, NamedExpression, OrOperator, XorOperator, AndOperator, NotOperator, AdditionOperator,
@@ -126,9 +125,9 @@ class ExpressionVisitor
           None, ParameterLookup, Identifier, PrimitiveLiteral, RegexMatch> {};
 
 template <class TResult>
-class QueryVisitor : public utils::Visitor<TResult, CypherQuery, ExplainQuery, ProfileQuery, IndexQuery, AuthQuery,
-                                           InfoQuery, ConstraintQuery, DumpQuery, ReplicationQuery, LockPathQuery,
-                                           FreeMemoryQuery, TriggerQuery, IsolationLevelQuery, CreateSnapshotQuery,
-                                           StreamQuery, SettingQuery, VersionQuery, ShowConfigQuery> {};
+class QueryVisitor
+    : public utils::Visitor<TResult, CypherQuery, ExplainQuery, ProfileQuery, IndexQuery, AuthQuery, InfoQuery,
+                            ConstraintQuery, DumpQuery, ReplicationQuery, LockPathQuery, FreeMemoryQuery, TriggerQuery,
+                            IsolationLevelQuery, CreateSnapshotQuery, StreamQuery, SettingQuery, VersionQuery> {};
 
 }  // namespace memgraph::query

src/query/frontend/ast/cypher_main_visitor.cpp

@@ -2353,11 +2353,6 @@ antlrcpp::Any CypherMainVisitor::visitForeach(MemgraphCypher::ForeachContext *ct
   return for_each;
 }
 
-antlrcpp::Any CypherMainVisitor::visitShowConfigQuery(MemgraphCypher::ShowConfigQueryContext * /*ctx*/) {
-  query_ = storage_->Create<ShowConfigQuery>();
-  return query_;
-}
-
 LabelIx CypherMainVisitor::AddLabel(const std::string &name) { return storage_->GetLabelIx(name); }
 
 PropertyIx CypherMainVisitor::AddProperty(const std::string &name) { return storage_->GetPropertyIx(name); }

src/query/frontend/ast/cypher_main_visitor.hpp

@@ -849,11 +849,6 @@ class CypherMainVisitor : public antlropencypher::MemgraphCypherBaseVisitor {
    */
   antlrcpp::Any visitForeach(MemgraphCypher::ForeachContext *ctx) override;
 
-  /**
-   * @return ShowConfigQuery*
-   */
-  antlrcpp::Any visitShowConfigQuery(MemgraphCypher::ShowConfigQueryContext *ctx) override;
-
  public:
   Query *query() { return query_; }
   const static std::string kAnonPrefix;

src/query/frontend/opencypher/grammar/MemgraphCypher.g4

@@ -122,7 +122,6 @@ query : cypherQuery
       | streamQuery
       | settingQuery
       | versionQuery
-      | showConfigQuery
       ;
 
 authQuery : createRole
@@ -373,6 +372,4 @@ showSetting : SHOW DATABASE SETTING settingName ;
 
 showSettings : SHOW DATABASE SETTINGS ;
 
-showConfigQuery : SHOW CONFIG ;
-
 versionQuery : SHOW VERSION ;

src/query/frontend/semantic/required_privileges.cpp

@@ -66,8 +66,6 @@ class PrivilegeExtractor : public QueryVisitor<void>, public HierarchicalTreeVis
 
   void Visit(FreeMemoryQuery &free_memory_query) override { AddPrivilege(AuthQuery::Privilege::FREE_MEMORY); }
 
-  void Visit(ShowConfigQuery & /*show_config_query*/) override { AddPrivilege(AuthQuery::Privilege::CONFIG); }
-
   void Visit(TriggerQuery &trigger_query) override { AddPrivilege(AuthQuery::Privilege::TRIGGER); }
 
   void Visit(StreamQuery &stream_query) override { AddPrivilege(AuthQuery::Privilege::STREAM); }

src/query/frontend/stripped_lexer_constants.hpp

@@ -204,8 +204,7 @@ const trie::Trie kKeywords = {"union",
                               "pulsar",
                               "service_url",
                               "version",
-                              "config",
-                              "websocket"
+                              "websocket",
                               "foreach"};
 
 // Unicode codepoints that are allowed at the start of the unescaped name.

src/query/interpret/awesome_memgraph_functions.cpp

@@ -1324,8 +1324,6 @@ std::function<TypedValue(const TypedValue *, int64_t, const FunctionContext &ctx
   if (function_name == "LOCALDATETIME") return LocalDateTime;
   if (function_name == "DURATION") return Duration;
 
-  // TODO(gitbuda): Add sum function.
-
   const auto &maybe_found =
       procedure::FindFunction(procedure::gModuleRegistry, function_name, utils::NewDeleteResource());
 

src/query/interpreter.cpp

@@ -20,7 +20,6 @@
 #include <functional>
 #include <limits>
 #include <optional>
-#include <variant>
 
 #include "glue/communication.hpp"
 #include "memory/memory_control.hpp"
@@ -76,9 +75,6 @@ extern const Event TriggersCreated;
 
 namespace memgraph::query {
 
-template <typename>
-constexpr auto kAlwaysFalse = false;
-
 namespace {
 void UpdateTypeCount(const plan::ReadWriteTypeChecker::RWType type) {
   switch (type) {
@@ -795,37 +791,6 @@ Callback HandleStreamQuery(StreamQuery *stream_query, const Parameters &paramete
   }
 }
 
-Callback HandleConfigQuery() {
-  Callback callback;
-  callback.header = {"name", "default_value", "current_value", "description"};
-
-  callback.fn = [] {
-    std::vector<GFLAGS_NAMESPACE::CommandLineFlagInfo> flags;
-    GetAllFlags(&flags);
-
-    std::vector<std::vector<TypedValue>> results;
-
-    for (const auto &flag : flags) {
-      if (flag.hidden ||
-          // These flags are not defined with gflags macros but are specified in config/flags.yaml
-          flag.name == "help" || flag.name == "help_xml" || flag.name == "version") {
-        continue;
-      }
-
-      std::vector<TypedValue> current_fields;
-      current_fields.emplace_back(flag.name);
-      current_fields.emplace_back(flag.default_value);
-      current_fields.emplace_back(flag.current_value);
-      current_fields.emplace_back(flag.description);
-
-      results.emplace_back(std::move(current_fields));
-    }
-
-    return results;
-  };
-  return callback;
-}
-
 Callback HandleSettingQuery(SettingQuery *setting_query, const Parameters &parameters, DbAccessor *db_accessor) {
   Frame frame(0);
   SymbolTable symbol_table;
@@ -1387,34 +1352,23 @@ PreparedQuery PrepareIndexQuery(ParsedQuery parsed_query, bool in_explicit_trans
       handler = [interpreter_context, label, properties_stringified = std::move(properties_stringified),
                  label_name = index_query->label_.name, properties = std::move(properties),
                  invalidate_plan_cache = std::move(invalidate_plan_cache)](Notification &index_notification) {
-        MG_ASSERT(properties.size() <= 1U);
-        auto maybe_index_error = properties.empty() ? interpreter_context->db->CreateIndex(label)
-                                                    : interpreter_context->db->CreateIndex(label, properties[0]);
-        utils::OnScopeExit invalidator(invalidate_plan_cache);
-
-        if (maybe_index_error.HasError()) {
-          const auto &error = maybe_index_error.GetError();
-          std::visit(
-              [&index_notification, &label_name, &properties_stringified]<typename T>(T &&) {
-                using ErrorType = std::remove_cvref_t<T>;
-                if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                  EventCounter::IncrementCounter(EventCounter::LabelIndexCreated);
-                  throw ReplicationException(
-                      fmt::format("At least one SYNC replica has not confirmed the creation of the index on label {} "
-                                  "on properties {}.",
-                                  label_name, properties_stringified));
-                } else if constexpr (std::is_same_v<ErrorType, storage::IndexDefinitionError>) {
-                  index_notification.code = NotificationCode::EXISTENT_INDEX;
-                  index_notification.title = fmt::format("Index on label {} on properties {} already exists.",
-                                                         label_name, properties_stringified);
-                } else {
-                  static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                }
-              },
-              error);
-        } else {
+        if (properties.empty()) {
+          if (!interpreter_context->db->CreateIndex(label)) {
+            index_notification.code = NotificationCode::EXISTANT_INDEX;
+            index_notification.title =
+                fmt::format("Index on label {} on properties {} already exists.", label_name, properties_stringified);
+          }
           EventCounter::IncrementCounter(EventCounter::LabelIndexCreated);
+        } else {
+          MG_ASSERT(properties.size() == 1U);
+          if (!interpreter_context->db->CreateIndex(label, properties[0])) {
+            index_notification.code = NotificationCode::EXISTANT_INDEX;
+            index_notification.title =
+                fmt::format("Index on label {} on properties {} already exists.", label_name, properties_stringified);
+          }
+          EventCounter::IncrementCounter(EventCounter::LabelPropertyIndexCreated);
         }
+        invalidate_plan_cache();
       };
       break;
     }
@@ -1425,31 +1379,21 @@ PreparedQuery PrepareIndexQuery(ParsedQuery parsed_query, bool in_explicit_trans
       handler = [interpreter_context, label, properties_stringified = std::move(properties_stringified),
                  label_name = index_query->label_.name, properties = std::move(properties),
                  invalidate_plan_cache = std::move(invalidate_plan_cache)](Notification &index_notification) {
-        MG_ASSERT(properties.size() <= 1U);
-        auto maybe_index_error = properties.empty() ? interpreter_context->db->DropIndex(label)
-                                                    : interpreter_context->db->DropIndex(label, properties[0]);
-        utils::OnScopeExit invalidator(invalidate_plan_cache);
-
-        if (maybe_index_error.HasError()) {
-          const auto &error = maybe_index_error.GetError();
-          std::visit(
-              [&index_notification, &label_name, &properties_stringified]<typename T>(T &&) {
-                using ErrorType = std::remove_cvref_t<T>;
-                if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                  throw ReplicationException(
-                      fmt::format("At least one SYNC replica has not confirmed the dropping of the index on label {} "
-                                  "on properties {}.",
-                                  label_name, properties_stringified));
-                } else if constexpr (std::is_same_v<ErrorType, storage::IndexDefinitionError>) {
-                  index_notification.code = NotificationCode::NONEXISTENT_INDEX;
-                  index_notification.title = fmt::format("Index on label {} on properties {} doesn't exist.",
-                                                         label_name, properties_stringified);
-                } else {
-                  static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                }
-              },
-              error);
+        if (properties.empty()) {
+          if (!interpreter_context->db->DropIndex(label)) {
+            index_notification.code = NotificationCode::NONEXISTANT_INDEX;
+            index_notification.title =
+                fmt::format("Index on label {} on properties {} doesn't exist.", label_name, properties_stringified);
+          }
+        } else {
+          MG_ASSERT(properties.size() == 1U);
+          if (!interpreter_context->db->DropIndex(label, properties[0])) {
+            index_notification.code = NotificationCode::NONEXISTANT_INDEX;
+            index_notification.title =
+                fmt::format("Index on label {} on properties {} doesn't exist.", label_name, properties_stringified);
+          }
         }
+        invalidate_plan_cache();
       };
       break;
     }
@@ -1577,28 +1521,6 @@ PreparedQuery PrepareFreeMemoryQuery(ParsedQuery parsed_query, const bool in_exp
       RWType::NONE};
 }
 
-PreparedQuery PrepareShowConfigQuery(ParsedQuery parsed_query, const bool in_explicit_transaction) {
-  if (in_explicit_transaction) {
-    throw ShowConfigModificationInMulticommandTxException();
-  }
-
-  auto callback = HandleConfigQuery();
-
-  return PreparedQuery{std::move(callback.header), std::move(parsed_query.required_privileges),
-                       [callback_fn = std::move(callback.fn), pull_plan = std::shared_ptr<PullPlanVector>{nullptr}](
-                           AnyStream *stream, std::optional<int> n) mutable -> std::optional<QueryHandlerResult> {
-                         if (!pull_plan) [[unlikely]] {
-                           pull_plan = std::make_shared<PullPlanVector>(callback_fn());
-                         }
-
-                         if (pull_plan->Pull(stream, n)) {
-                           return QueryHandlerResult::COMMIT;
-                         }
-                         return std::nullopt;
-                       },
-                       RWType::NONE};
-}
-
 TriggerEventType ToTriggerEventType(const TriggerQuery::EventType event_type) {
   switch (event_type) {
     case TriggerQuery::EventType::ANY:
@@ -1998,37 +1920,21 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
           handler = [interpreter_context, label, label_name = constraint_query->constraint_.label.name,
                      properties_stringified = std::move(properties_stringified),
                      properties = std::move(properties)](Notification &constraint_notification) {
-            auto maybe_constraint_error = interpreter_context->db->CreateExistenceConstraint(label, properties[0]);
-
-            if (maybe_constraint_error.HasError()) {
-              const auto &error = maybe_constraint_error.GetError();
-              std::visit(
-                  [&interpreter_context, &label_name, &properties_stringified,
-                   &constraint_notification]<typename T>(T &&arg) {
-                    using ErrorType = std::remove_cvref_t<T>;
-                    if constexpr (std::is_same_v<ErrorType, storage::ConstraintViolation>) {
-                      auto &violation = arg;
-                      MG_ASSERT(violation.properties.size() == 1U);
-                      auto property_name = interpreter_context->db->PropertyToName(*violation.properties.begin());
-                      throw QueryRuntimeException(
-                          "Unable to create existence constraint :{}({}), because an "
-                          "existing node violates it.",
-                          label_name, property_name);
-                    } else if constexpr (std::is_same_v<ErrorType, storage::ConstraintDefinitionError>) {
-                      constraint_notification.code = NotificationCode::EXISTENT_CONSTRAINT;
-                      constraint_notification.title =
-                          fmt::format("Constraint EXISTS on label {} on properties {} already exists.", label_name,
-                                      properties_stringified);
-                    } else if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                      throw ReplicationException(
-                          "At least one SYNC replica has not confirmed the creation of the EXISTS constraint on label "
-                          "{} on properties {}.",
-                          label_name, properties_stringified);
-                    } else {
-                      static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                    }
-                  },
-                  error);
+            auto res = interpreter_context->db->CreateExistenceConstraint(label, properties[0]);
+            if (res.HasError()) {
+              auto violation = res.GetError();
+              auto label_name = interpreter_context->db->LabelToName(violation.label);
+              MG_ASSERT(violation.properties.size() == 1U);
+              auto property_name = interpreter_context->db->PropertyToName(*violation.properties.begin());
+              throw QueryRuntimeException(
+                  "Unable to create existence constraint :{}({}), because an "
+                  "existing node violates it.",
+                  label_name, property_name);
+            }
+            if (res.HasValue() && !res.GetValue()) {
+              constraint_notification.code = NotificationCode::EXISTANT_CONSTRAINT;
+              constraint_notification.title = fmt::format(
+                  "Constraint EXISTS on label {} on properties {} already exists.", label_name, properties_stringified);
             }
           };
           break;
@@ -2046,35 +1952,21 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
           handler = [interpreter_context, label, label_name = constraint_query->constraint_.label.name,
                      properties_stringified = std::move(properties_stringified),
                      property_set = std::move(property_set)](Notification &constraint_notification) {
-            auto maybe_constraint_error = interpreter_context->db->CreateUniqueConstraint(label, property_set);
-            if (maybe_constraint_error.HasError()) {
-              const auto &error = maybe_constraint_error.GetError();
-              std::visit(
-                  [&interpreter_context, &label_name, &properties_stringified]<typename T>(T &&arg) {
-                    using ErrorType = std::remove_cvref_t<T>;
-                    if constexpr (std::is_same_v<ErrorType, storage::ConstraintViolation>) {
-                      auto &violation = arg;
-                      auto violation_label_name = interpreter_context->db->LabelToName(violation.label);
-                      std::stringstream property_names_stream;
-                      utils::PrintIterable(property_names_stream, violation.properties, ", ",
-                                           [&interpreter_context](auto &stream, const auto &prop) {
-                                             stream << interpreter_context->db->PropertyToName(prop);
-                                           });
-                      throw QueryRuntimeException(
-                          "Unable to create unique constraint :{}({}), because an "
-                          "existing node violates it.",
-                          violation_label_name, property_names_stream.str());
-                    } else if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                      throw ReplicationException(fmt::format(
-                          "At least one SYNC replica has not confirmed the creation of the UNIQUE constraint: {}({}).",
-                          label_name, properties_stringified));
-                    } else {
-                      static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                    }
-                  },
-                  error);
+            auto res = interpreter_context->db->CreateUniqueConstraint(label, property_set);
+            if (res.HasError()) {
+              auto violation = res.GetError();
+              auto label_name = interpreter_context->db->LabelToName(violation.label);
+              std::stringstream property_names_stream;
+              utils::PrintIterable(property_names_stream, violation.properties, ", ",
+                                   [&interpreter_context](auto &stream, const auto &prop) {
+                                     stream << interpreter_context->db->PropertyToName(prop);
+                                   });
+              throw QueryRuntimeException(
+                  "Unable to create unique constraint :{}({}), because an "
+                  "existing node violates it.",
+                  label_name, property_names_stream.str());
             }
-            switch (maybe_constraint_error.GetValue()) {
+            switch (res.GetValue()) {
               case storage::UniqueConstraints::CreationStatus::EMPTY_PROPERTIES:
                 throw SyntaxException(
                     "At least one property must be used for unique "
@@ -2085,7 +1977,7 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
                     "for unique constraints is exceeded.",
                     storage::kUniqueConstraintsMaxProperties);
               case storage::UniqueConstraints::CreationStatus::ALREADY_EXISTS:
-                constraint_notification.code = NotificationCode::EXISTENT_CONSTRAINT;
+                constraint_notification.code = NotificationCode::EXISTANT_CONSTRAINT;
                 constraint_notification.title =
                     fmt::format("Constraint UNIQUE on label {} on properties {} already exists.", label_name,
                                 properties_stringified);
@@ -2113,27 +2005,10 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
           handler = [interpreter_context, label, label_name = constraint_query->constraint_.label.name,
                      properties_stringified = std::move(properties_stringified),
                      properties = std::move(properties)](Notification &constraint_notification) {
-            auto maybe_constraint_error = interpreter_context->db->DropExistenceConstraint(label, properties[0]);
-            if (maybe_constraint_error.HasError()) {
-              const auto &error = maybe_constraint_error.GetError();
-              std::visit(
-                  [&label_name, &properties_stringified, &constraint_notification]<typename T>(T &&) {
-                    using ErrorType = std::remove_cvref_t<T>;
-                    if constexpr (std::is_same_v<ErrorType, storage::ConstraintDefinitionError>) {
-                      constraint_notification.code = NotificationCode::NONEXISTENT_CONSTRAINT;
-                      constraint_notification.title =
-                          fmt::format("Constraint EXISTS on label {} on properties {} doesn't exist.", label_name,
-                                      properties_stringified);
-                    } else if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                      throw ReplicationException(
-                          fmt::format("At least one SYNC replica has not confirmed the dropping of the EXISTS "
-                                      "constraint  on label {} on properties {}.",
-                                      label_name, properties_stringified));
-                    } else {
-                      static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                    }
-                  },
-                  error);
+            if (!interpreter_context->db->DropExistenceConstraint(label, properties[0])) {
+              constraint_notification.code = NotificationCode::NONEXISTANT_CONSTRAINT;
+              constraint_notification.title = fmt::format(
+                  "Constraint EXISTS on label {} on properties {} doesn't exist.", label_name, properties_stringified);
             }
             return std::vector<std::vector<TypedValue>>();
           };
@@ -2152,24 +2027,7 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
           handler = [interpreter_context, label, label_name = constraint_query->constraint_.label.name,
                      properties_stringified = std::move(properties_stringified),
                      property_set = std::move(property_set)](Notification &constraint_notification) {
-            auto maybe_constraint_error = interpreter_context->db->DropUniqueConstraint(label, property_set);
-            if (maybe_constraint_error.HasError()) {
-              const auto &error = maybe_constraint_error.GetError();
-              std::visit(
-                  [&label_name, &properties_stringified]<typename T>(T &&) {
-                    using ErrorType = std::remove_cvref_t<T>;
-                    if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-                      throw ReplicationException(
-                          fmt::format("At least one SYNC replica has not confirmed the dropping of the UNIQUE "
-                                      "constraint on label {} on properties {}.",
-                                      label_name, properties_stringified));
-                    } else {
-                      static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-                    }
-                  },
-                  error);
-            }
-            const auto &res = maybe_constraint_error.GetValue();
+            auto res = interpreter_context->db->DropUniqueConstraint(label, property_set);
             switch (res) {
               case storage::UniqueConstraints::DeletionStatus::EMPTY_PROPERTIES:
                 throw SyntaxException(
@@ -2183,7 +2041,7 @@ PreparedQuery PrepareConstraintQuery(ParsedQuery parsed_query, bool in_explicit_
                     storage::kUniqueConstraintsMaxProperties);
                 break;
               case storage::UniqueConstraints::DeletionStatus::NOT_FOUND:
-                constraint_notification.code = NotificationCode::NONEXISTENT_CONSTRAINT;
+                constraint_notification.code = NotificationCode::NONEXISTANT_CONSTRAINT;
                 constraint_notification.title =
                     fmt::format("Constraint UNIQUE on label {} on properties {} doesn't exist.", label_name,
                                 properties_stringified);
@@ -2323,8 +2181,6 @@ Interpreter::PrepareResult Interpreter::Prepare(const std::string &query_string,
                                             &*execution_db_accessor_);
     } else if (utils::Downcast<FreeMemoryQuery>(parsed_query.query)) {
       prepared_query = PrepareFreeMemoryQuery(std::move(parsed_query), in_explicit_transaction_, interpreter_context_);
-    } else if (utils::Downcast<ShowConfigQuery>(parsed_query.query)) {
-      prepared_query = PrepareShowConfigQuery(std::move(parsed_query), in_explicit_transaction_);
     } else if (utils::Downcast<TriggerQuery>(parsed_query.query)) {
       prepared_query =
           PrepareTriggerQuery(std::move(parsed_query), in_explicit_transaction_, &query_execution->notifications,
@@ -2401,41 +2257,28 @@ void RunTriggersIndividually(const utils::SkipList<Trigger> &triggers, Interpret
       continue;
     }
 
-    auto maybe_commit_error = db_accessor.Commit();
-    if (maybe_commit_error.HasError()) {
-      const auto &error = maybe_commit_error.GetError();
-
-      std::visit(
-          [&trigger, &db_accessor]<typename T>(T &&arg) {
-            using ErrorType = std::remove_cvref_t<T>;
-            if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-              spdlog::warn("At least one SYNC replica has not confirmed execution of the trigger '{}'.",
-                           trigger.Name());
-            } else if constexpr (std::is_same_v<ErrorType, storage::ConstraintViolation>) {
-              const auto &constraint_violation = arg;
-              switch (constraint_violation.type) {
-                case storage::ConstraintViolation::Type::EXISTENCE: {
-                  const auto &label_name = db_accessor.LabelToName(constraint_violation.label);
-                  MG_ASSERT(constraint_violation.properties.size() == 1U);
-                  const auto &property_name = db_accessor.PropertyToName(*constraint_violation.properties.begin());
-                  spdlog::warn("Trigger '{}' failed to commit due to existence constraint violation on: {}({}) ",
-                               trigger.Name(), label_name, property_name);
-                }
-                case storage::ConstraintViolation::Type::UNIQUE: {
-                  const auto &label_name = db_accessor.LabelToName(constraint_violation.label);
-                  std::stringstream property_names_stream;
-                  utils::PrintIterable(
-                      property_names_stream, constraint_violation.properties, ", ",
-                      [&](auto &stream, const auto &prop) { stream << db_accessor.PropertyToName(prop); });
-                  spdlog::warn("Trigger '{}' failed to commit due to unique constraint violation on :{}({})",
-                               trigger.Name(), label_name, property_names_stream.str());
-                }
-              }
-            } else {
-              static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-            }
-          },
-          error);
+    auto maybe_constraint_violation = db_accessor.Commit();
+    if (maybe_constraint_violation.HasError()) {
+      const auto &constraint_violation = maybe_constraint_violation.GetError();
+      switch (constraint_violation.type) {
+        case storage::ConstraintViolation::Type::EXISTENCE: {
+          const auto &label_name = db_accessor.LabelToName(constraint_violation.label);
+          MG_ASSERT(constraint_violation.properties.size() == 1U);
+          const auto &property_name = db_accessor.PropertyToName(*constraint_violation.properties.begin());
+          spdlog::warn("Trigger '{}' failed to commit due to existence constraint violation on :{}({})", trigger.Name(),
+                       label_name, property_name);
+          break;
+        }
+        case storage::ConstraintViolation::Type::UNIQUE: {
+          const auto &label_name = db_accessor.LabelToName(constraint_violation.label);
+          std::stringstream property_names_stream;
+          utils::PrintIterable(property_names_stream, constraint_violation.properties, ", ",
+                               [&](auto &stream, const auto &prop) { stream << db_accessor.PropertyToName(prop); });
+          spdlog::warn("Trigger '{}' failed to commit due to unique constraint violation on :{}({})", trigger.Name(),
+                       label_name, property_names_stream.str());
+          break;
+        }
+      }
     }
   }
 }
@@ -2476,45 +2319,32 @@ void Interpreter::Commit() {
     db_accessor_.reset();
     trigger_context_collector_.reset();
   };
-  utils::OnScopeExit members_reseter(reset_necessary_members);
 
-  auto commit_confirmed_by_all_sync_repplicas = true;
-
-  auto maybe_commit_error = db_accessor_->Commit();
-  if (maybe_commit_error.HasError()) {
-    const auto &error = maybe_commit_error.GetError();
-
-    std::visit(
-        [&execution_db_accessor = execution_db_accessor_,
-         &commit_confirmed_by_all_sync_repplicas]<typename T>(T &&arg) {
-          using ErrorType = std::remove_cvref_t<T>;
-          if constexpr (std::is_same_v<ErrorType, storage::ReplicationError>) {
-            commit_confirmed_by_all_sync_repplicas = false;
-          } else if constexpr (std::is_same_v<ErrorType, storage::ConstraintViolation>) {
-            const auto &constraint_violation = arg;
-            auto &label_name = execution_db_accessor->LabelToName(constraint_violation.label);
-            switch (constraint_violation.type) {
-              case storage::ConstraintViolation::Type::EXISTENCE: {
-                MG_ASSERT(constraint_violation.properties.size() == 1U);
-                auto &property_name = execution_db_accessor->PropertyToName(*constraint_violation.properties.begin());
-                throw QueryException("Unable to commit due to existence constraint violation on :{}({})", label_name,
-                                     property_name);
-              }
-              case storage::ConstraintViolation::Type::UNIQUE: {
-                std::stringstream property_names_stream;
-                utils::PrintIterable(property_names_stream, constraint_violation.properties, ", ",
-                                     [&execution_db_accessor](auto &stream, const auto &prop) {
-                                       stream << execution_db_accessor->PropertyToName(prop);
-                                     });
-                throw QueryException("Unable to commit due to unique constraint violation on :{}({})", label_name,
-                                     property_names_stream.str());
-              }
-            }
-          } else {
-            static_assert(kAlwaysFalse<T>, "Missing type from variant visitor");
-          }
-        },
-        error);
+  auto maybe_constraint_violation = db_accessor_->Commit();
+  if (maybe_constraint_violation.HasError()) {
+    const auto &constraint_violation = maybe_constraint_violation.GetError();
+    switch (constraint_violation.type) {
+      case storage::ConstraintViolation::Type::EXISTENCE: {
+        auto label_name = execution_db_accessor_->LabelToName(constraint_violation.label);
+        MG_ASSERT(constraint_violation.properties.size() == 1U);
+        auto property_name = execution_db_accessor_->PropertyToName(*constraint_violation.properties.begin());
+        reset_necessary_members();
+        throw QueryException("Unable to commit due to existence constraint violation on :{}({})", label_name,
+                             property_name);
+        break;
+      }
+      case storage::ConstraintViolation::Type::UNIQUE: {
+        auto label_name = execution_db_accessor_->LabelToName(constraint_violation.label);
+        std::stringstream property_names_stream;
+        utils::PrintIterable(
+            property_names_stream, constraint_violation.properties, ", ",
+            [this](auto &stream, const auto &prop) { stream << execution_db_accessor_->PropertyToName(prop); });
+        reset_necessary_members();
+        throw QueryException("Unable to commit due to unique constraint violation on :{}({})", label_name,
+                             property_names_stream.str());
+        break;
+      }
+    }
   }
 
   // The ordered execution of after commit triggers is heavily depending on the exclusiveness of db_accessor_->Commit():
@@ -2533,10 +2363,9 @@ void Interpreter::Commit() {
         });
   }
 
+  reset_necessary_members();
+
   SPDLOG_DEBUG("Finished committing the transaction");
-  if (!commit_confirmed_by_all_sync_repplicas) {
-    throw ReplicationException("At least one SYNC replica has not confirmed committing last transaction.");
-  }
 }
 
 void Interpreter::AdvanceCommand() {

src/query/metadata.cpp

@@ -52,15 +52,15 @@ constexpr std::string_view GetCodeString(const NotificationCode code) {
       return "DropStream"sv;
     case NotificationCode::DROP_TRIGGER:
       return "DropTrigger"sv;
-    case NotificationCode::EXISTENT_CONSTRAINT:
+    case NotificationCode::EXISTANT_CONSTRAINT:
       return "ConstraintAlreadyExists"sv;
-    case NotificationCode::EXISTENT_INDEX:
+    case NotificationCode::EXISTANT_INDEX:
       return "IndexAlreadyExists"sv;
     case NotificationCode::LOAD_CSV_TIP:
       return "LoadCSVTip"sv;
-    case NotificationCode::NONEXISTENT_INDEX:
+    case NotificationCode::NONEXISTANT_INDEX:
       return "IndexDoesNotExist"sv;
-    case NotificationCode::NONEXISTENT_CONSTRAINT:
+    case NotificationCode::NONEXISTANT_CONSTRAINT:
       return "ConstraintDoesNotExist"sv;
     case NotificationCode::REGISTER_REPLICA:
       return "RegisterReplica"sv;

src/query/metadata.hpp

@@ -34,11 +34,11 @@ enum class NotificationCode : uint8_t {
   DROP_REPLICA,
   DROP_STREAM,
   DROP_TRIGGER,
-  EXISTENT_INDEX,
-  EXISTENT_CONSTRAINT,
+  EXISTANT_INDEX,
+  EXISTANT_CONSTRAINT,
   LOAD_CSV_TIP,
-  NONEXISTENT_INDEX,
-  NONEXISTENT_CONSTRAINT,
+  NONEXISTANT_INDEX,
+  NONEXISTANT_CONSTRAINT,
   REPLICA_PORT_WARNING,
   REGISTER_REPLICA,
   SET_REPLICA,

src/query/plan/operator.cpp

@@ -368,13 +368,12 @@ VertexAccessor &CreateExpand::CreateExpandCursor::OtherVertex(Frame &frame, Exec
     TypedValue &dest_node_value = frame[self_.node_info_.symbol];
     ExpectType(self_.node_info_.symbol, dest_node_value, TypedValue::Type::Vertex);
     return dest_node_value.ValueVertex();
-  } else {
-    auto &created_vertex = CreateLocalVertex(self_.node_info_, &frame, context);
-    if (context.trigger_context_collector) {
-      context.trigger_context_collector->RegisterCreatedObject(created_vertex);
-    }
-    return created_vertex;
   }
+  auto &created_vertex = CreateLocalVertex(self_.node_info_, &frame, context);
+  if (context.trigger_context_collector) {
+    context.trigger_context_collector->RegisterCreatedObject(created_vertex);
+  }
+  return created_vertex;
 }
 
 template <class TVerticesFun>

src/query/plan/rewrite/index_lookup.cpp

@@ -13,12 +13,11 @@
 
 #include "utils/flag_validation.hpp"
 
-// NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_VALIDATED_int64(query_vertex_count_to_expand_existing, 10,
-                       "Maximum count of indexed vertices which provoke "
-                       "indexed lookup and then expand to existing, instead of "
-                       "a regular expand. Default is 10, to turn off use -1.",
-                       FLAG_IN_RANGE(-1, std::numeric_limits<std::int64_t>::max()));
+DEFINE_VALIDATED_HIDDEN_int64(query_vertex_count_to_expand_existing, 10,
+                              "Maximum count of indexed vertices which provoke "
+                              "indexed lookup and then expand to existing, instead of "
+                              "a regular expand. Default is 10, to turn off use -1.",
+                              FLAG_IN_RANGE(-1, std::numeric_limits<std::int64_t>::max()));
 
 namespace memgraph::query::plan::impl {
 

src/query/plan/variable_start_planner.cpp

@@ -17,9 +17,8 @@
 #include "utils/flag_validation.hpp"
 #include "utils/logging.hpp"
 
-// NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
-DEFINE_VALIDATED_uint64(query_max_plans, 1000U, "Maximum number of generated plans for a query.",
-                        FLAG_IN_RANGE(1, std::numeric_limits<std::uint64_t>::max()));
+DEFINE_VALIDATED_HIDDEN_uint64(query_max_plans, 1000U, "Maximum number of generated plans for a query.",
+                               FLAG_IN_RANGE(1, std::numeric_limits<std::uint64_t>::max()));
 
 namespace memgraph::query::plan::impl {
 

src/query/procedure/mg_procedure_impl.cpp

@@ -2796,29 +2796,3 @@ mgp_error mgp_module_add_function(mgp_module *module, const char *name, mgp_func
       },
       result);
 }
-
-mgp_error mgp_log(const mgp_log_level log_level, const char *output) {
-  return WrapExceptions([=] {
-    switch (log_level) {
-      case mgp_log_level::MGP_LOG_LEVEL_TRACE:
-        spdlog::trace(output);
-        return;
-      case mgp_log_level::MGP_LOG_LEVEL_DEBUG:
-        spdlog::debug(output);
-        return;
-      case mgp_log_level::MGP_LOG_LEVEL_INFO:
-        spdlog::info(output);
-        return;
-      case mgp_log_level::MGP_LOG_LEVEL_WARN:
-        spdlog::warn(output);
-        return;
-      case mgp_log_level::MGP_LOG_LEVEL_ERROR:
-        spdlog::error(output);
-        return;
-      case mgp_log_level::MGP_LOG_LEVEL_CRITICAL:
-        spdlog::critical(output);
-        return;
-    }
-    throw std::invalid_argument{fmt::format("Invalid log level: {}", log_level)};
-  });
-}

src/query/procedure/py_module.cpp

@@ -2052,81 +2052,6 @@ PyObject *PyPathMakeWithStart(PyTypeObject *type, PyObject *vertex) {
   return py_path;
 }
 
-// clang-format off
-struct PyLogger {
-  PyObject_HEAD
-};
-// clang-format on
-
-PyObject *PyLoggerLog(PyLogger *self, PyObject *args, const mgp_log_level level) {
-  MG_ASSERT(self);
-  const char *out = nullptr;
-  if (!PyArg_ParseTuple(args, "s", &out)) {
-    return nullptr;
-  }
-
-  if (RaiseExceptionFromErrorCode(mgp_log(level, out))) {
-    return nullptr;
-  }
-
-  Py_RETURN_NONE;
-}
-
-PyObject *PyLoggerLogInfo(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_INFO);
-}
-
-PyObject *PyLoggerLogWarning(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_WARN);
-}
-
-PyObject *PyLoggerLogError(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_ERROR);
-}
-
-PyObject *PyLoggerLogCritical(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_CRITICAL);
-}
-
-PyObject *PyLoggerLogTrace(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_TRACE);
-}
-
-PyObject *PyLoggerLogDebug(PyLogger *self, PyObject *args) {
-  return PyLoggerLog(self, args, mgp_log_level::MGP_LOG_LEVEL_DEBUG);
-}
-
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-static PyMethodDef PyLoggerMethods[] = {
-    {"__reduce__", reinterpret_cast<PyCFunction>(DisallowPickleAndCopy), METH_NOARGS, "__reduce__ is not supported"},
-    {"info", reinterpret_cast<PyCFunction>(PyLoggerLogInfo), METH_VARARGS,
-     "Logs a message with level INFO on this logger."},
-    {"warning", reinterpret_cast<PyCFunction>(PyLoggerLogWarning), METH_VARARGS,
-     "Logs a message with level WARNNING on this logger."},
-    {"error", reinterpret_cast<PyCFunction>(PyLoggerLogError), METH_VARARGS,
-     "Logs a message with level ERROR on this logger."},
-    {"critical", reinterpret_cast<PyCFunction>(PyLoggerLogCritical), METH_VARARGS,
-     "Logs a message with level CRITICAL on this logger."},
-    {"trace", reinterpret_cast<PyCFunction>(PyLoggerLogTrace), METH_VARARGS,
-     "Logs a message with level TRACE on this logger."},
-    {"debug", reinterpret_cast<PyCFunction>(PyLoggerLogDebug), METH_VARARGS,
-     "Logs a message with level DEBUG on this logger."},
-    {nullptr},
-};
-
-// clang-format off
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-static PyTypeObject PyLoggerType = {
-    PyVarObject_HEAD_INIT(nullptr, 0)
-    .tp_name = "_mgp.Logger",
-    .tp_basicsize = sizeof(PyLogger),
-    // NOLINTNEXTLINE(hicpp-signed-bitwise)
-    .tp_flags = Py_TPFLAGS_DEFAULT,
-    .tp_doc = "Logging API.",
-    .tp_methods = PyLoggerMethods,
-};
-// clang-format on
-
 struct PyMgpError {
   const char *name;
   PyObject *&exception;
@@ -2178,7 +2103,6 @@ PyObject *PyInitMgpModule() {
   if (!register_type(&PyCypherTypeType, "Type")) return nullptr;
   if (!register_type(&PyMessagesType, "Messages")) return nullptr;
   if (!register_type(&PyMessageType, "Message")) return nullptr;
-  if (!register_type(&PyLoggerType, "Logger")) return nullptr;
 
   std::array py_mgp_errors{
       PyMgpError{"_mgp.UnknownError", gMgpUnknownError, PyExc_RuntimeError, nullptr},
@@ -2245,14 +2169,8 @@ auto WithMgpModule(mgp_module *module_def, const TFun &fun) {
             "import a new module. Is some other thread also importing Python "
             "modules?");
   auto *py_query_module = MakePyQueryModule(module_def);
-
   MG_ASSERT(py_query_module);
   MG_ASSERT(py_mgp.SetAttr("_MODULE", py_query_module));
-
-  // NOLINTNEXTLINE(cppcoreguidelines-pro-type-cstyle-cast)
-  auto *py_logger = reinterpret_cast<PyObject *>(PyObject_New(PyLogger, &PyLoggerType));
-  MG_ASSERT(py_mgp.SetAttr("_LOGGER", py_logger));
-
   auto ret = fun();
   auto maybe_exc = py::FetchError();
   MG_ASSERT(py_mgp.SetAttr("_MODULE", Py_None));

src/query/v2/CMakeLists.txt

@@ -0,0 +1,59 @@
+define_add_lcp(add_lcp_query lcp_query_v2_cpp_files generated_lcp_query_v2_files)
+
+add_lcp_query(frontend/ast/ast.lcp)
+add_lcp_query(plan/operator.lcp)
+
+add_custom_target(generate_lcp_query_v2 DEPENDS ${generated_lcp_query_v2_files})
+
+set(mg_query_v2_sources
+    ${lcp_query_v2_cpp_files}
+    common.cpp
+    cypher_query_interpreter.cpp
+    dump.cpp
+    frontend/semantic/required_privileges.cpp
+    frontend/stripped.cpp
+    interpret/awesome_memgraph_functions.cpp
+    interpreter.cpp
+    metadata.cpp
+    plan/operator.cpp
+    plan/preprocess.cpp
+    plan/pretty_print.cpp
+    plan/profile.cpp
+    plan/read_write_type_checker.cpp
+    plan/rewrite/index_lookup.cpp
+    plan/rule_based_planner.cpp
+    plan/variable_start_planner.cpp
+    #    procedure/mg_procedure_impl.cpp
+    #    procedure/mg_procedure_helpers.cpp
+    #    procedure/module.cpp
+    #    procedure/py_module.cpp
+    serialization/property_value.cpp
+    #    stream/streams.cpp
+    #    stream/sources.cpp
+    #    stream/common.cpp
+    #    trigger.cpp
+    #    trigger_context.cpp
+    bindings/typed_value.cpp
+    accessors.cpp)
+
+find_package(Boost REQUIRED)
+
+add_library(mg-query-v2 STATIC ${mg_query_v2_sources})
+add_dependencies(mg-query-v2 generate_lcp_query_v2)
+target_include_directories(mg-query-v2 PUBLIC ${CMAKE_SOURCE_DIR}/include)
+target_include_directories(mg-query-v2 PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/bindings)
+target_link_libraries(mg-query-v2 dl cppitertools Boost::headers)
+target_link_libraries(mg-query-v2 mg-integrations-pulsar mg-integrations-kafka mg-storage-v3 mg-license mg-utils mg-kvstore mg-memory)
+target_link_libraries(mg-query-v2 mg-expr)
+
+if(NOT "${MG_PYTHON_PATH}" STREQUAL "")
+    set(Python3_ROOT_DIR "${MG_PYTHON_PATH}")
+endif()
+
+if("${MG_PYTHON_VERSION}" STREQUAL "")
+    find_package(Python3 3.5 REQUIRED COMPONENTS Development)
+else()
+    find_package(Python3 "${MG_PYTHON_VERSION}" EXACT REQUIRED COMPONENTS Development)
+endif()
+
+target_link_libraries(mg-query-v2 Python3::Python)

src/query/v2/accessors.cpp

@@ -0,0 +1,75 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#include "query/v2/accessors.hpp"
+#include "query/v2/requests.hpp"
+
+namespace memgraph::query::v2::accessors {
+EdgeAccessor::EdgeAccessor(Edge edge, std::vector<std::pair<PropertyId, Value>> props)
+    : edge(std::move(edge)), properties(std::move(props)) {}
+
+uint64_t EdgeAccessor::EdgeType() const { return edge.type.id; }
+
+std::vector<std::pair<PropertyId, Value>> EdgeAccessor::Properties() const {
+  return properties;
+  //    std::map<std::string, TypedValue> res;
+  //    for (const auto &[name, value] : *properties) {
+  //      res[name] = ValueToTypedValue(value);
+  //    }
+  //    return res;
+}
+
+// NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+Value EdgeAccessor::GetProperty(const std::string & /*prop_name*/) const {
+  // TODO(kostasrim) fix this
+  return {};
+}
+
+Edge EdgeAccessor::GetEdge() const { return edge; }
+
+VertexAccessor EdgeAccessor::To() const { return VertexAccessor(Vertex{edge.dst}, {}); }
+
+VertexAccessor EdgeAccessor::From() const { return VertexAccessor(Vertex{edge.src}, {}); }
+
+VertexAccessor::VertexAccessor(Vertex v, std::vector<std::pair<PropertyId, Value>> props)
+    : vertex(std::move(v)), properties(std::move(props)) {}
+
+std::vector<Label> VertexAccessor::Labels() const { return vertex.labels; }
+
+bool VertexAccessor::HasLabel(Label &label) const {
+  return std::find_if(vertex.labels.begin(), vertex.labels.end(),
+                      [label](const auto &l) { return l.id == label.id; }) != vertex.labels.end();
+}
+
+std::vector<std::pair<PropertyId, Value>> VertexAccessor::Properties() const {
+  //    std::map<std::string, TypedValue> res;
+  //    for (const auto &[name, value] : *properties) {
+  //      res[name] = ValueToTypedValue(value);
+  //    }
+  //    return res;
+  return properties;
+}
+
+Value VertexAccessor::GetProperty(PropertyId prop_id) const {
+  return std::find_if(properties.begin(), properties.end(), [&](auto &pr) { return prop_id == pr.first; })->second;
+  //    return ValueToTypedValue(properties[prop_name]);
+}
+
+// NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+Value VertexAccessor::GetProperty(const std::string & /*prop_name*/) const {
+  // TODO(kostasrim) Add string mapping
+  return {};
+  //    return ValueToTypedValue(properties[prop_name]);
+}
+
+msgs::Vertex VertexAccessor::GetVertex() const { return vertex; }
+
+}  // namespace memgraph::query::v2::accessors

src/query/v2/accessors.hpp

@@ -0,0 +1,187 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include <optional>
+#include <utility>
+#include <vector>
+
+#include "query/exceptions.hpp"
+#include "query/v2/requests.hpp"
+#include "storage/v3/view.hpp"
+#include "utils/bound.hpp"
+#include "utils/exceptions.hpp"
+#include "utils/memory.hpp"
+#include "utils/memory_tracker.hpp"
+
+namespace memgraph::query::v2::accessors {
+
+using Value = memgraph::msgs::Value;
+using Edge = memgraph::msgs::Edge;
+using Vertex = memgraph::msgs::Vertex;
+using Label = memgraph::msgs::Label;
+using PropertyId = memgraph::msgs::PropertyId;
+
+class VertexAccessor;
+
+class EdgeAccessor final {
+ public:
+  EdgeAccessor(Edge edge, std::vector<std::pair<PropertyId, Value>> props);
+
+  uint64_t EdgeType() const;
+
+  std::vector<std::pair<PropertyId, Value>> Properties() const;
+
+  Value GetProperty(const std::string &prop_name) const;
+
+  Edge GetEdge() const;
+
+  // Dummy function
+  // NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+  inline size_t CypherId() const { return 10; }
+
+  //  bool HasSrcAccessor const { return src == nullptr; }
+  //  bool HasDstAccessor const { return dst == nullptr; }
+
+  VertexAccessor To() const;
+  VertexAccessor From() const;
+
+  friend bool operator==(const EdgeAccessor &lhs, const EdgeAccessor &rhs) {
+    return lhs.edge == rhs.edge && lhs.properties == rhs.properties;
+  }
+
+  friend bool operator!=(const EdgeAccessor &lhs, const EdgeAccessor &rhs) { return !(lhs == rhs); }
+
+ private:
+  Edge edge;
+  std::vector<std::pair<PropertyId, Value>> properties;
+};
+
+class VertexAccessor final {
+ public:
+  using PropertyId = msgs::PropertyId;
+  using Label = msgs::Label;
+  VertexAccessor(Vertex v, std::vector<std::pair<PropertyId, Value>> props);
+
+  std::vector<Label> Labels() const;
+
+  bool HasLabel(Label &label) const;
+
+  std::vector<std::pair<PropertyId, Value>> Properties() const;
+
+  Value GetProperty(PropertyId prop_id) const;
+  Value GetProperty(const std::string &prop_name) const;
+
+  msgs::Vertex GetVertex() const;
+
+  // Dummy function
+  // NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+  inline size_t CypherId() const { return 10; }
+
+  //  auto InEdges(storage::View view, const std::vector<storage::EdgeTypeId> &edge_types) const
+  //      -> storage::Result<decltype(iter::imap(MakeEdgeAccessor, *impl_.InEdges(view)))> {
+  //    auto maybe_edges = impl_.InEdges(view, edge_types);
+  //    if (maybe_edges.HasError()) return maybe_edges.GetError();
+  //    return iter::imap(MakeEdgeAccessor, std::move(*maybe_edges));
+  //  }
+  //
+  //  auto InEdges(storage::View view) const { return InEdges(view, {}); }
+  //
+  //  auto InEdges(storage::View view, const std::vector<storage::EdgeTypeId> &edge_types, const VertexAccessor &dest)
+  //  const
+  //      -> storage::Result<decltype(iter::imap(MakeEdgeAccessor, *impl_.InEdges(view)))> {
+  //    auto maybe_edges = impl_.InEdges(view, edge_types, &dest.impl_);
+  //    if (maybe_edges.HasError()) return maybe_edges.GetError();
+  //    return iter::imap(MakeEdgeAccessor, std::move(*maybe_edges));
+  //  }
+  //
+  //  auto OutEdges(storage::View view, const std::vector<storage::EdgeTypeId> &edge_types) const
+  //      -> storage::Result<decltype(iter::imap(MakeEdgeAccessor, *impl_.OutEdges(view)))> {
+  //    auto maybe_edges = impl_.OutEdges(view, edge_types);
+  //    if (maybe_edges.HasError()) return maybe_edges.GetError();
+  //    return iter::imap(MakeEdgeAccessor, std::move(*maybe_edges));
+  //  }
+  //
+  //  auto OutEdges(storage::View view) const { return OutEdges(view, {}); }
+  //
+  //  auto OutEdges(storage::View view, const std::vector<storage::EdgeTypeId> &edge_types,
+  //                const VertexAccessor &dest) const
+  //      -> storage::Result<decltype(iter::imap(MakeEdgeAccessor, *impl_.OutEdges(view)))> {
+  //    auto maybe_edges = impl_.OutEdges(view, edge_types, &dest.impl_);
+  //    if (maybe_edges.HasError()) return maybe_edges.GetError();
+  //    return iter::imap(MakeEdgeAccessor, std::move(*maybe_edges));
+  //  }
+
+  //  storage::Result<size_t> InDegree(storage::View view) const { return impl_.InDegree(view); }
+  //
+  //  storage::Result<size_t> OutDegree(storage::View view) const { return impl_.OutDegree(view); }
+  //
+
+  friend bool operator==(const VertexAccessor &lhs, const VertexAccessor &rhs) {
+    return lhs.vertex == rhs.vertex && lhs.properties == rhs.properties;
+  }
+
+  friend bool operator!=(const VertexAccessor &lhs, const VertexAccessor &rhs) { return !(lhs == rhs); }
+
+ private:
+  Vertex vertex;
+  std::vector<std::pair<PropertyId, Value>> properties;
+};
+
+// inline VertexAccessor EdgeAccessor::To() const { return VertexAccessor(impl_.ToVertex()); }
+
+// inline VertexAccessor EdgeAccessor::From() const { return VertexAccessor(impl_.FromVertex()); }
+
+// Highly mocked interface. Won't work if used.
+class Path {
+ public:
+  // Empty for now
+  explicit Path(const VertexAccessor & /*vertex*/, utils::MemoryResource *memory = utils::NewDeleteResource())
+      : mem(memory) {}
+
+  template <typename... TOthers>
+  explicit Path(const VertexAccessor &vertex, const TOthers &...others) {}
+
+  template <typename... TOthers>
+  Path(std::allocator_arg_t /*unused*/, utils::MemoryResource *memory, const VertexAccessor &vertex,
+       const TOthers &...others) {}
+
+  Path(const Path & /*other*/) {}
+
+  Path(const Path & /*other*/, utils::MemoryResource *memory) : mem(memory) {}
+
+  Path(Path && /*other*/) noexcept {}
+
+  Path(Path && /*other*/, utils::MemoryResource *memory) : mem(memory) {}
+  Path &operator=(const Path &path) {
+    if (this == &path) {
+      return *this;
+    }
+    return *this;
+  }
+
+  Path &operator=(Path &&path) noexcept {
+    if (this == &path) {
+      return *this;
+    }
+    return *this;
+  }
+
+  ~Path() {}
+
+  friend bool operator==(const Path & /*lhs*/, const Path & /*rhs*/) { return true; };
+  utils::MemoryResource *GetMemoryResource() { return mem; }
+
+ private:
+  utils::MemoryResource *mem = utils::NewDeleteResource();
+};
+}  // namespace memgraph::query::v2::accessors

src/query/v2/auth_checker.hpp

@@ -0,0 +1,29 @@
+// Copyright 2022 Memgraph Ltd.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
+// License, and you may not use this file except in compliance with the Business Source License.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+#pragma once
+
+#include "query/v2/frontend/ast/ast.hpp"
+
+namespace memgraph::query::v2 {
+class AuthChecker {
+ public:
+  virtual bool IsUserAuthorized(const std::optional<std::string> &username,
+                                const std::vector<query::v2::AuthQuery::Privilege> &privileges) const = 0;
+};
+
+class AllowEverythingAuthChecker final : public query::v2::AuthChecker {
+  bool IsUserAuthorized(const std::optional<std::string> & /*username*/,
+                        const std::vector<query::v2::AuthQuery::Privilege> & /*privileges*/) const override {
+    return true;
+  }
+};
+}  // namespace memgraph::query::v2