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Add nested pattern comprehension #3169

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Merged
Josipmrden merged 2 commits into from
Aug 7, 2025
Merged

Add nested pattern comprehension #3169

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8a08799
Add nested pattern comprehension
Josipmrden Aug 7, 2025
f1d5db2
Fix test
Josipmrden Aug 7, 2025
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9 changes: 9 additions & 0 deletions src/query/plan/preprocess.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1151,6 +1151,15 @@ void PatternVisitor::Visit(NamedExpression &op) { op.expression_->Accept(*this);
void PatternVisitor::Visit(PatternComprehension &op) {
PatternComprehensionMatching matching;
AddMatching({op.pattern_}, op.filter_, symbol_table_, storage_, matching);

for (auto &filter : matching.filters) {
PatternVisitor nested_visitor(symbol_table_, storage_);

filter.expression->Accept(nested_visitor);
filter.matchings = nested_visitor.getFilterMatchings();
filter.pattern_comprehension_matchings = nested_visitor.getPatternComprehensionMatchings();
}

matching.result_expr = storage_.Create<NamedExpression>(symbol_table_.at(op).name(), op.resultExpr_);
matching.result_expr->MapTo(symbol_table_.at(op));
matching.result_symbol = symbol_table_.at(op);
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16 changes: 16 additions & 0 deletions tests/gql_behave/tests/memgraph_V1/features/list_comprehension.feature
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Expand Up @@ -146,3 +146,19 @@ Feature: ListComprehension
MATCH (a) WHERE single(x in [(a)-[:R]->(b) WHERE b is null | 1] WHERE true) RETURN a.id AS id
"""
Then the result should be empty

Scenario: Pattern comprehension in list comprehension - double nested
Given an empty graph
And having executed:
"""
CREATE (a:A {id: 1})<-[:R1]-(:B)<-[:R2]-(:C)<-[:R3]-(:D {id: 1});
"""
When executing query:
"""
MATCH (a:A)
WHERE single(b IN [(a)<-[:R1]-(b:B) WHERE single(c IN [(b)<-[:R2]-(c:C) WHERE single(d IN [(c)<-[:R3]-(d:D) WHERE d.id = 1 | 1] WHERE true) | 1] WHERE true) | 1] WHERE true)
RETURN a.id AS id;
"""
Then the result should be:
| id |
| 1 |
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