PG compatibility: baseline policy and deterministic CI cases (Task 6)

[renecannao]

Context

This issue tracks Task 6 from docs/superpowers/plans/2026-06-11-postgresql-libpg-query-compatibility.md and follows #48.

Goal

Implement baseline transition evaluation and deterministic pull-request case generation for the PostgreSQL compatibility harness.

Implemented

• Added scripts/pg_compat/baseline.py.
• Added tests/pg_compat/test_baseline.py.
• Added transition_allowed(previous, current) with the complete six-result policy.
• Added evaluate_baseline(previous_rows, current_rows) with deterministic allowed, regressions, review_required, new_cases, and missing_ids output.
• Added build_ci_cases(inventory_rows, release_delta_rows, witness_rows).
• Added atomic, sorted JSONL publication through write_ci_cases(path, cases).
• Added duplicate-ID, conflicting-case, invalid-result, missing-SQL, input-order, and input-mutation validation coverage.

Transition policy

Allowed transitions:

• unchanged result
• any result to DEEP_SUPPORTED
• PARTIAL, ERROR, TRAILING_INPUT, or TYPE_MISMATCH to CLASSIFIED_ONLY

Disallowed support-level drops are reported as regressions. Other disallowed result changes are reported as review-required. Unknown current IDs require baseline refresh; missing IDs are reported separately.

CI case selection

The generated set deterministically includes:

• every known non-DEEP_SUPPORTED result
• every release-delta statement
• every reviewed witness
• one DEEP_SUPPORTED and one CLASSIFIED_ONLY example per oracle node where available

Cases are deduplicated, sorted by statement ID, retain complete SQL, and include expected_result.

Verification

• Focused suite: 9 tests passed.
• Full PostgreSQL compatibility suite with the PG18 runner: 73 tests passed.
• Commit: bcc707b feat: enforce PostgreSQL compatibility baselines
• Pull request: [codex] PostgreSQL compatibility harness foundation #50

Status

Implementation is complete on PR #50. The issue will close when that PR merges.

[coderabbitai]

🔗 Related PRs

#38 - fix(set): handle PostgreSQL SET TIME ZONE alias and multi-value lists [merged]
#39 - fix(set): coverage for ProxySQL set_parser_algorithm=3 audit (P1..P6) [merged]

---

📝 Issue Planner

_{Check the box below or use the @coderabbitai plan command to generate an implementation plan and prompts that you can use with your favorite coding assistant.}

• Create Plan

---

🧪 Issue enrichment is currently in open beta.

You can configure auto-planning by selecting labels in the issue_enrichment configuration.

To disable automatic issue enrichment, add the following to your .coderabbit.yaml:

issue_enrichment:
  auto_enrich:
    enabled: false

💬 Have feedback or questions? Drop into our discord!

[renecannao]

Task 6 was implemented and pushed in commit bcc707b. Local verification passed: 9 focused baseline tests and 73 full PostgreSQL compatibility tests using the PG18 runner. Fresh PR CI is now running on #50.

[renecannao]

Fresh CI for Task 6 commit bcc707b completed successfully: 8 checks passed, with 0 failing, 0 cancelled, and 0 pending.