OpenCypher Pattern Implementation Status¶
Implementation status of OpenCypher pattern matching features in GraphForge.
Legend: ✅ COMPLETE | ⚠️ PARTIAL | ❌ NOT_IMPLEMENTED
Summary¶
| Pattern Type | Status | Notes |
|---|---|---|
| Node Patterns | ✅ COMPLETE | All variations supported |
| Relationship Patterns | ✅ COMPLETE | Direction, types, properties |
| Variable-Length Paths | ✅ COMPLETE | All quantifier forms |
| Path Variables | ✅ COMPLETE | Path binding supported |
| Pattern Predicates | ✅ COMPLETE | WHERE predicates in patterns fully supported |
| Optional Patterns | ✅ COMPLETE | OPTIONAL MATCH |
| Pattern Comprehension | ✅ COMPLETE | All forms supported |
| Multiple Patterns | ✅ COMPLETE | Comma-separated patterns |
Overall: 8/8 pattern types complete (100%)
Node Patterns¶
Empty Node () ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Match scenarios
Node with Variable (n) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Match scenarios
Node with Label (:Label) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Extensive Match scenarios
Node with Variable and Label (n:Label) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Match scenarios
Multiple Labels (n:Label1:Label2) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Label scenarios
Node with Properties ({prop: value}) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Property matching scenarios
Combined (n:Label {prop: value}) ✅¶
Status: COMPLETE
Grammar: cypher.lark:109
Tests: Match scenarios
Relationship Patterns¶
Undirected -[]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:115
Executor: executor.py:554 (_execute_expand)
Tests: Match scenarios
Directed → ✅¶
Status: COMPLETE
Grammar: cypher.lark:117
Tests: Match scenarios
Directed ← ✅¶
Status: COMPLETE
Grammar: cypher.lark:116
Tests: Match scenarios
With Variable -[r]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:115
Tests: Match scenarios
With Type -[:TYPE]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:115
Tests: Match scenarios
With Variable and Type -[r:TYPE]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:115
Tests: Match scenarios
With Properties -[{prop: value}]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:115
Tests: Match scenarios
Multiple Types -[:TYPE1|TYPE2]- ✅¶
Status: COMPLETE Grammar: Relationship type parsing Tests: Type union scenarios
Variable-Length Paths¶
Unbounded -[*]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:124
Executor: executor.py:820 (_execute_variable_expand)
Tests: Variable-length scenarios
Fixed Range -[*n..m]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:121
Tests: Variable-length scenarios
Min Only -[*n..]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:122
Tests: Variable-length scenarios
Max Only -[*..m]- ✅¶
Status: COMPLETE
Grammar: cypher.lark:123
Tests: Variable-length scenarios
With Type -[:TYPE*]- ✅¶
Status: COMPLETE Grammar: Combined type and length Tests: Variable-length with type
With Properties -[*{prop: value}]- ✅¶
Status: COMPLETE Grammar: Combined properties and length Tests: Variable-length with properties
Path Variables¶
Path Binding (path = (a)-[]->(b)) ✅¶
Status: COMPLETE
Grammar: cypher.lark:104
Tests: Path binding scenarios
Path Functions (length, nodes, relationships) ✅¶
Status: COMPLETE Executor: Path function evaluation Tests: Path function scenarios
Pattern Predicates¶
Inline WHERE (WHERE r.weight > 5) ✅¶
Status: COMPLETE
Grammar: cypher.lark:119 (pattern_where rule)
Parser: parser.py:481-484 (RelationshipPattern.predicate field)
Executor: executor.py:617-622 (_execute_expand), executor.py:904-918 (_execute_variable_expand)
Tests: tests/integration/test_pattern_predicates.py (16 comprehensive tests)
Supported features: - Property comparisons (r.since > 2020) - Complex expressions (AND, OR, NOT) - Function calls in predicates (length(r.name) = 3) - NULL handling (predicates with missing properties) - Variable-length paths with predicates - Undirected relationships with predicates - Multiple patterns with different predicates - Combination with external WHERE clauses
Notes: Full openCypher pattern predicate support implemented and tested. All 16 integration tests passing.
Optional Patterns¶
OPTIONAL MATCH ✅¶
Status: COMPLETE
Grammar: cypher.lark:72
Executor: executor.py:483 (_execute_optional_scan)
Tests: Optional match scenarios with NULL handling
Pattern Comprehension¶
[(pattern) WHERE condition | expression] ✅¶
Status: COMPLETE
Grammar: cypher.lark:263 (pattern_comprehension rule)
Parser: parser.py:1047-1068 (pattern_comprehension transformer)
Evaluator: evaluator.py:559-591 (PatternComprehension evaluation)
Tests: tests/integration/test_pattern_comprehension.py (15 comprehensive tests)
Supported features:
- Simple node patterns: [(p:Person) | p.name]
- Relationship patterns: [(p)-[:KNOWS]->(f) | f.name]
- WITH WHERE filters: [(p:Person) WHERE p.age > 18 | p.name]
- Complex expressions: [(p:Person) | p.age * 2]
- Nested in RETURN, WHERE, WITH clauses
- Multiple pattern comprehensions in one query
- Correlated variables from outer scope
- NULL property handling
Notes: Full pattern comprehension support implemented. Pattern matching is executed for each input row, with results collected into a list. All 15 integration tests passing.
Multiple Patterns¶
Comma-Separated Patterns ✅¶
Status: COMPLETE
Grammar: cypher.lark:69 (MATCH supports multiple patterns)
Tests: Multiple pattern scenarios
Multiple MATCH Clauses ✅¶
Status: COMPLETE Grammar: Query structure supports chaining Tests: Chained MATCH scenarios
Implementation Notes¶
Strengths¶
- Comprehensive node matching: All label and property combinations
- Full relationship support: All directions, types, and properties
- Variable-length paths: All quantifier forms with proper termination
- Path variables: Binding and path function support
- Pattern predicates: Complete WHERE predicate support in patterns
- Pattern comprehensions: Full support for pattern-based list operations
- OPTIONAL patterns: Complete NULL-handling outer join semantics
Limitations¶
- Quantified path patterns: New GQL spec feature not yet in OpenCypher
Implementation Quality¶
- Parser: Comprehensive pattern grammar coverage
- Planner: Efficient operator generation for patterns
- Executor: Robust pattern matching with proper semantics
- Tests: Extensive TCK coverage for all pattern types
Priority for v0.4.0+¶
- Low: Quantified path patterns (new GQL spec)
Version History¶
- v0.1.0: Basic node and relationship patterns
- v0.2.0: Variable-length paths, path variables
- v0.3.0: OPTIONAL MATCH, pattern predicates (partial), multiple patterns
- v0.3.3: Pattern predicates (complete), pattern comprehension (complete)
References¶
- OpenCypher Specification: https://opencypher.org/resources/
- GraphForge Grammar:
src/graphforge/parser/cypher.lark - GraphForge Executor:
src/graphforge/executor/executor.py - GraphForge Planner:
src/graphforge/planner/planner.py