chore(cysql): add postgresql property index plan regression tests - BED-8505

[zinic]

Description

Add property index regression tests to cover translation changes that may change query forms where index matching is essential.

Resolves: BED-8505

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
• Full test suite run (make test_all with CONNECTION_STRING set)

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

• Documentation

  • Clarified CySQL's suffix/substring indexing behavior for CONTAINS, STARTS WITH, and ENDS WITH patterns.
  • Added regression test documentation for PostgreSQL property index validation.

• Tests

  • Expanded string predicate tests to cover literal patterns with index verification.
  • Added new integration tests validating PostgreSQL query plans utilize configured property indexes.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 628de4bf-4c15-4447-be6f-c429fcc2ffd5

📥 Commits

Reviewing files that changed from the base of the PR and between 7df86c0 and fe1c744.

📒 Files selected for processing (4)

• README.md
• cypher/Cypher Syntax Support.md
• cypher/models/pgsql/translate/predicate_test.go
• integration/pgsql_property_index_plan_test.go

Walkthrough

This PR adds comprehensive PostgreSQL property index plan regression testing. Documentation defines the index-match contract; unit tests validate that specific string predicates translate to index-compatible SQL; and a manual integration test verifies query plans actually use configured B-tree and GIN trigram indexes when executing Cypher predicates on node properties.

Changes

PostgreSQL Property Index Plan Testing

Layer / File(s)	Summary
Documentation and Index Contract README.md, cypher/Cypher Syntax Support.md	README documents the manual integration test requirement and invocation; Cypher Syntax Support narrows the index-match contract to literal CONTAINS, STARTS WITH, ENDS WITH lowered to LIKE, explicitly excluding dynamic helper-lowered forms.
Unit Test Assertions for Index-Compatible Translation cypher/models/pgsql/translate/predicate_test.go	Refactored TestLiteralStringPredicatesKeepLikePatterns into a table-driven test for literal string predicates; added TestStringPropertyEqualityKeepsBTreeIndexableTextLookup to validate that string equality translates to jsonb_typeof guards and B-tree-indexable text lookups without helper functions or coercion.
Integration Test Entry Point and PostgreSQL Setup integration/pgsql_property_index_plan_test.go	New manual integration test file; TestPostgreSQLPropertyIndexPlans runs B-tree and trigram sub-suites; setupIndexedPostgresDB initializes the indexed Dawgs graph, asserts schema, and registers cleanup.
B-tree Equality Index Testing with Fixtures integration/pgsql_property_index_plan_test.go	B-tree sub-suite tests CONTAINS and equality predicates on objectid field; fixtures create targeted nodes; analyzeIndexedNodePartition updates planner stats; assertTranslatedPlanUsesIndex verifies plan uses expected index; negative control mutates SQL to confirm index miss.
GIN Trigram Text Search Index Testing integration/pgsql_property_index_plan_test.go	GIN trigram sub-suite tests STARTS WITH, ENDS WITH, CONTAINS on name field; assertMutatedTranslatedPlanMissesIndex mutates translated SQL and confirms the trigram index is no longer used.
Test Infrastructure: Translation, EXPLAIN, and Plan Inspection integration/pgsql_property_index_plan_test.go	Helper functions: translateIndexedCypher translates Cypher to SQL; explainWithSeqScanDisabled runs PostgreSQL EXPLAIN; normalizeExplainPlan decodes EXPLAIN JSON; planContainsIndex recursively searches for index names; replaceSQLExpressionOnce mutates SQL for negative tests; formatPlanForFailure formats plans for assertion output.

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested Labels

go

Poem

🐰 A test hops in to check the plans,
Making sure each index spans,
B-trees and trigrams, side by side,
PostgreSQL's query hopes won't hide! 🥕

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: adding PostgreSQL property index plan regression tests, with a reference to the ticket BED-8505.
Description check	✅ Passed	The description is substantially complete, addressing the motivation, type of change, testing performed, and driver impact. All major template sections are filled appropriately.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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