fix(cysql): ensure that optional matches are only rendered with valid previous frame - BED-7054

[zinic]

Description

Missed a check where the optional keyword was encountered with no previous query frame present.

Resolves: BED-7054

Type of Change

• Chore (a change that does not modify the application functionality)
• Bug fix (a change that fixes an issue)
• New feature / enhancement (a change that adds new functionality)
• Refactor (no behaviour change)
• Test coverage
• Build / CI / tooling
• Documentation

Testing

• Unit tests added / updated
• Integration tests added / updated
• Manual integration tests run (go test -tags manual_integration ./integration/...)

Driver Impact

• PostgreSQL driver (drivers/pg)
• Neo4j driver (drivers/neo4j)

Checklist

• Code is formatted
• All existing tests pass
• go.mod / go.sum are up to date if dependencies changed

Summary by CodeRabbit

• Tests

  • Added test case for optional match patterns returning nodes with zero matching incoming relationships.

• Bug Fixes

  • Enhanced optional match translation to properly validate scope context, improving accuracy for complex graph queries.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

Walkthrough

A new optional match translation test case is added for scenarios with zero matching edges, and the optional match translation logic is refined to validate previous frames before proceeding with aggregation rather than checking for mere frame existence.

Changes

Cohort / File(s)	Summary
Optional Match Test Case cypher/models/pgsql/test/translation_cases/multipart.sql	Added test case for optional match pattern returning nodes when zero matching incoming edges exist, using grouped subquery with count filter.
Optional Match Translation Logic cypher/models/pgsql/translate/match.go	Modified translateMatch to conditionally invoke translateOptionalMatch() only when previousValidFrame() indicates a valid previous frame, replacing direct Previous frame existence check.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A rabbit hops through query trees,
Where optional matches dance with ease,
Now counting edges, finding none,
Valid frames make logic run,
Zero matches, perfect spree! 🌟

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: fixing optional match rendering to require a valid previous frame, with relevant ticket reference BED-7054.
Description check	✅ Passed	The description covers all required sections with appropriate information: clear summary of the fix, ticket reference, bug fix classification, test updates confirmed, PostgreSQL driver impact noted, and all checklist items completed.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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