prototype implementation

src/query/frontend/ast/ast.lcp

@@ -398,7 +398,7 @@ cpp<#
                ,@(loop for op in
                        '(or-operator xor-operator and-operator addition-operator
                          subtraction-operator multiplication-operator division-operator
-                         mod-operator not-equal-operator equal-operator less-operator
+                         mod-operator not-equal-operator less-operator
                          greater-operator less-equal-operator greater-equal-operator
                          in-list-operator subscript-operator)
                        collecting
@@ -458,6 +458,33 @@ cpp<#
                           (:clone))))))
   (define-unary-operators))
 
+(lcp:define-class equal-operator (binary-operator)
+  ((isNullCheckRequired "bool" :initval "false" :scope :public))
+  (:public
+    #>cpp
+    DEFVISITABLE(ExpressionVisitor<TypedValue>);
+    DEFVISITABLE(ExpressionVisitor<void>);
+
+    bool Accept(HierarchicalTreeVisitor &visitor) override {
+      if (visitor.PreVisit(*this)) {
+        expression1_->Accept(visitor) && expression2_->Accept(visitor);
+      }
+      return visitor.PostVisit(*this);
+    }
+    cpp<#)
+  (:protected
+    #>cpp
+    using BinaryOperator::BinaryOperator;
+    EqualOperator(Expression *expression1, Expression *expression2, bool is_nullcheck_required = false)
+        : BinaryOperator(expression1, expression2), isnullcheckrequired_(is_nullcheck_required) {}
+    cpp<#)
+  (:private
+    #>cpp
+    friend class AstStorage;
+    cpp<#)
+  (:serialize (:slk))
+  (:clone))
+
 (lcp:define-class aggregation (binary-operator)
   ((op "Op" :scope :public)
    (symbol-pos :int32_t :initval -1 :scope :public

src/query/frontend/ast/cypher_main_visitor.cpp

@@ -2267,9 +2267,9 @@ antlrcpp::Any CypherMainVisitor::visitCaseExpression(MemgraphCypher::CaseExpress
   Expression *else_expression = ctx->else_expression ? ctx->else_expression->accept(this).as<Expression *>()
                                                      : storage_->Create<PrimitiveLiteral>(TypedValue());
   for (auto *alternative : alternatives) {
-    Expression *condition =
-        test_expression ? storage_->Create<EqualOperator>(test_expression, alternative->when_expression->accept(this))
-                        : alternative->when_expression->accept(this).as<Expression *>();
+    Expression *condition = test_expression ? storage_->Create<EqualOperator>(
+                                                  test_expression, alternative->when_expression->accept(this), true)
+                                            : alternative->when_expression->accept(this).as<Expression *>();
     Expression *then_expression = alternative->then_expression->accept(this);
     else_expression = storage_->Create<IfOperator>(condition, then_expression, else_expression);
   }

src/query/interpret/eval.hpp

@@ -81,7 +81,7 @@ class ExpressionEvaluator : public ExpressionVisitor<TypedValue> {
   BINARY_OPERATOR_VISITOR(DivisionOperator, /, /);
   BINARY_OPERATOR_VISITOR(ModOperator, %, %);
   BINARY_OPERATOR_VISITOR(NotEqualOperator, !=, <>);
-  BINARY_OPERATOR_VISITOR(EqualOperator, ==, =);
+  // BINARY_OPERATOR_VISITOR(EqualOperator, ==, =);
   BINARY_OPERATOR_VISITOR(LessOperator, <, <);
   BINARY_OPERATOR_VISITOR(GreaterOperator, >, >);
   BINARY_OPERATOR_VISITOR(LessEqualOperator, <=, <=);
@@ -94,6 +94,29 @@ class ExpressionEvaluator : public ExpressionVisitor<TypedValue> {
 #undef BINARY_OPERATOR_VISITOR
 #undef UNARY_OPERATOR_VISITOR
 
+  TypedValue Visit(EqualOperator &op) override {
+    auto val1 = op.expression1_->Accept(*this);
+    auto val2 = op.expression2_->Accept(*this);
+
+    // if(val1.IsNull())
+    // {
+    //   val1.V
+    // }
+
+    // if(op.isoperandnull_)
+    //   throw QueryRuntimeException("Use the generic form when checking against NULL.");
+
+    try {
+      if (op.isnullcheckrequired_ && val2.IsNull()) {
+        throw QueryRuntimeException("Use the generic form when checking against NULL.");
+      }
+
+      return val1 == val2;
+    } catch (const TypedValueException &) {
+      throw QueryRuntimeException("Invalid types: {} and {} for '='.", val1.type(), val2.type());
+    }
+  }
+
   TypedValue Visit(AndOperator &op) override {
     auto value1 = op.expression1_->Accept(*this);
     if (value1.IsBool() && !value1.ValueBool()) {

tests/unit/cypher_main_visitor.cpp

@@ -790,6 +790,26 @@ TEST_P(CypherMainVisitorTest, CaseSimpleForm) {
   ast_generator.CheckLiteral(if_operator->else_expression_, TypedValue());
 }
 
+TEST_P(CypherMainVisitorTest, CaseSimpleFormNullcheckIsSet) {
+  auto &ast_generator = *GetParam();
+  auto *query = dynamic_cast<CypherQuery *>(ast_generator.ParseQuery("RETURN CASE 5 WHEN 10 THEN 1 END"));
+  ASSERT_TRUE(query);
+  ASSERT_TRUE(query->single_query_);
+  auto *single_query = query->single_query_;
+  auto *return_clause = dynamic_cast<Return *>(single_query->clauses_[0]);
+  auto *if_operator = dynamic_cast<IfOperator *>(return_clause->body_.named_expressions[0]->expression_);
+  auto *condition = dynamic_cast<EqualOperator *>(if_operator->condition_);
+  ASSERT_TRUE(condition);
+  ast_generator.CheckLiteral(condition->expression1_, 5);
+  ast_generator.CheckLiteral(condition->expression2_, 10);
+
+  // This might be the only line thats different.
+  ASSERT_TRUE(condition->isnullcheckrequired_);
+
+  ast_generator.CheckLiteral(if_operator->then_expression_, 1);
+  ast_generator.CheckLiteral(if_operator->else_expression_, TypedValue());
+}
+
 TEST_P(CypherMainVisitorTest, IsNull) {
   auto &ast_generator = *GetParam();
   auto *query = dynamic_cast<CypherQuery *>(ast_generator.ParseQuery("RETURN 2 iS NulL"));