Map symbols to expansions to speed up variable planning

Summary:
Test variable planning BFS.
Add more tests for variably planning ExpandVariable.
Don't recreate the whole matching when varying expansions.
Use explicit constructors in private planner classes.

Reviewers: mislav.bradac, florijan

Reviewed By: mislav.bradac

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D691

tests/benchmark/query/planner.cpp

@@ -0,0 +1,50 @@
+#include <string>
+
+#include <benchmark/benchmark_api.h>
+
+#include "database/dbms.hpp"
+#include "query/frontend/semantic/symbol_generator.hpp"
+#include "query/plan/planner.hpp"
+
+// Add chained MATCH (node1) -- (node2), MATCH (node2) -- (node3) ... clauses.
+static void AddMatches(int num_matches, query::AstTreeStorage &storage) {
+  for (int i = 0; i < num_matches; ++i) {
+    auto *match = storage.Create<query::Match>();
+    auto *pattern = storage.Create<query::Pattern>();
+    pattern->identifier_ = storage.Create<query::Identifier>("path");
+    match->patterns_.emplace_back(pattern);
+    std::string node1_name = "node" + std::to_string(i - 1);
+    pattern->atoms_.emplace_back(storage.Create<query::NodeAtom>(
+        storage.Create<query::Identifier>(node1_name)));
+    pattern->atoms_.emplace_back(storage.Create<query::EdgeAtom>(
+        storage.Create<query::Identifier>("edge" + std::to_string(i)),
+        query::EdgeAtom::Direction::BOTH));
+    pattern->atoms_.emplace_back(storage.Create<query::NodeAtom>(
+        storage.Create<query::Identifier>("node" + std::to_string(i))));
+    storage.query()->clauses_.emplace_back(match);
+  }
+}
+
+static void BM_MakeLogicalPlan(benchmark::State &state) {
+  while (state.KeepRunning()) {
+    state.PauseTiming();
+    Dbms dbms;
+    auto dba = dbms.active();
+    query::AstTreeStorage storage;
+    int num_matches = state.range(0);
+    AddMatches(num_matches, storage);
+    query::SymbolTable symbol_table;
+    query::SymbolGenerator symbol_generator(symbol_table);
+    storage.query()->Accept(symbol_generator);
+    state.ResumeTiming();
+    query::plan::MakeLogicalPlan<query::plan::VariableStartPlanner>(
+        storage, symbol_table, *dba);
+  }
+};
+
+BENCHMARK(BM_MakeLogicalPlan)
+    ->RangeMultiplier(2)
+    ->Range(50, 400)
+    ->Unit(benchmark::kMillisecond);
+
+BENCHMARK_MAIN();