Test improvement for OID cast index scan optimization

[RuchaSK1]

Description

Cherry-picked from : #4872

This PR addresses review feedback from the OID cast index scan optimization PR that was merged earlier:

1. Include ordering: Adjusted as per alphabetical position
2. Removed InsertExecContext typedef and function declarations from pltsql.h that were included as part of the cherry-pick from 6x. - Not applicable here
3. Volatile function test: Added a test case verifying that the contain_volatile_functions guard correctly prevents index optimization when the comparison value is volatile (e.g., random()). The test disables sequential scan to prove the hook definitively blocks the index path rather than the planner simply preferring a different plan on cost.

Regarding other AI review comments:

• 500 schemas (Issue 3): The count was determined through testing to ensure consistent Index Scan plans across both local and CI environments. Reducing it causes plan instability. Additionally, it serves as a stress test that helps surface stale-stats issues in upgrade paths. If it causes timeout issues in future, the count can be reduced.
• EXPLAIN fragility (Issue 4): Acknowledged. Plan shapes may change across PostgreSQL major versions and will be updated if needed.

Issues Resolved

Task: BABEL-6814
Authored-by: Rucha Kulkarni ruchask@amazon.com
Signed-off-by: Rucha Kulkarni ruchask@amazon.com

Test Scenarios Covered

• Use case based - Yes

• Boundary conditions -

• Arbitrary inputs -

• Negative test cases - Yes

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Check List

• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is under the terms of the Apache 2.0 and PostgreSQL licenses, and grant any person obtaining a copy of the contribution permission to relicense all or a portion of my contribution to the PostgreSQL License solely to contribute all or a portion of my contribution to the PostgreSQL open source project.

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[RuchaSK1]

/code-review

[kuntalghosh]

AI Code Review

Verdict: APPROVE

Based on the provided code changes, here are my feedback and suggestions:

This PR addresses review feedback from the OID cast index scan optimization (PR #4868) with two clean changes:

1. Include reordering in hooks.c — Pure alphabetical sorting of #include directives. No headers were added or removed; the set of included headers is identical before and after. No executable code was changed.

2. Volatile function test (Test 23) — Well-constructed regression test that disables sequential scan, queries with random()::int (a volatile expression), and verifies the planner produces a "Seq Scan (Disabled: true)" rather than an Index Scan. This proves the contain_volatile_functions guard in the hook correctly prevents the OID cast index optimization when the comparison value is volatile.

No blocking issues found.

Issue 1 (Advisory) - PR Description: Empty test scenario checklist:

The "Test Scenarios Covered" section in the PR template has all bullet items left blank. While the description body adequately explains the test being added (volatile function guard verification), filling in at least the "Use case based" bullet would improve clarity for future readers.

Notes

• Security review completed on hooks.c: 0 findings. The change is a pure include reordering with no security impact.
• The test correctly restores enable_seqscan to on after the test, preventing state leakage to subsequent tests.
• Both standard and parallel_query expected output files are updated consistently.
• Cherry-picked from PR #4872 targeting a different branch — base branch BABEL_6_X_DEV is appropriate.

Note: This AI review is meant to augment, not replace, human review. Use the suggestions with discretion.