feat (pg): introduce edge start/end with kind filter index - BED-7853

[zinic]

Description

Introduce an index that accelerates start_id and kind_id filters for edge lookups. This is one of the most common lookups during traversal.

This includes some over-eager index removal that are only adding to the write-amplification problem. The graph_id indexes are covered by the graph_id column being part of the partition key.

Resolves: BED-7853

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/...)

Screenshots (if appropriate):

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

• Chores
  • Optimized database query performance to speed up multi-criteria filtering and retrieval.
  • Users should notice snappier responses when performing searches and viewing related data, improving overall application responsiveness.

[coderabbitai]

Walkthrough

Replaced single-column B-tree indexes on node(graph_id) and edge(graph_id) with explicit drops and added two composite B-tree indexes on edge: edge_start_kind_index(start_id, kind_id) and edge_end_kind_index(end_id, kind_id); existing single-column indexes on edge(start_id), edge(end_id), and edge(kind_id) remain.

Changes

Cohort / File(s)	Summary
Database Schema drivers/pg/query/sql/schema_up.sql	Dropped single-column indexes on node(graph_id) and edge(graph_id) and added composite B-tree indexes edge_start_kind_index(start_id, kind_id) and edge_end_kind_index(end_id, kind_id). Existing edge(start_id), edge(end_id), and edge(kind_id) indexes kept intact.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I nibble lines of SQL bright,

I pair up keys beneath moonlight,
Start and End with Kind in tune,
Queries hum beneath the moon,
Hop—indexes make speed take flight!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: introducing composite indexes on edge table for start/end_id with kind_id filtering, which is the primary objective of this PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The pull request description follows the template structure with all required sections completed, including description, type of change, testing, driver impact, and checklist items.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[StephenHinck]

Would you mind indicating in the PR description that we also dropped these indices? Otherwise, this looks good.