test(dal): pin t9's plan to the identity index

[LKSNDRTMLKV]

main went red on the testcontainers job: t9_find_by_identity_matches_draft_and_published_via_index took 10.149s against the 10s budget in scripts/slow-test-check.sh. On the eight runs before it the same test took 0.9–3.1s.

The time was the setup, not the lookup. The test inserted 200 decoy passports, one commit each, so that the table was big enough for the planner to prefer an index over a sequential scan. Two hundred fsyncs on a busy runner is what crossed the line.

The plan check now prices sequential scans out instead (SET LOCAL enable_seqscan = off in a transaction), which holds at any table size. A disabled seq scan still shows in the plan when no index can serve the query, so the existing !plan.contains("Seq Scan") assertion keeps its meaning.

The plan assertion also names the index now. It used to accept any Index Scan, and two other indexes qualify: idx_passport_identifier covers the same identifier expression, and idx_passport_status the status filter. Checked locally by dropping idx_passport_identity before the EXPLAIN: the planner switched to Index Scan using idx_passport_identifier, which the old assertion passes and the new one fails.

The EXPLAIN now runs the statement find_by_identity actually sends: its serialNumber predicate and ORDER BY created_at were missing, and a LIMIT 1 it never had was present, which changes what the planner optimises for. The same drop-the-index check fails on that shape too (Sort over Index Scan using idx_passport_identifier).

The 200 decoys become two that each differ from a real row by one key: the draft's identifier under another batch, and the draft's batch under the published passport's identifier. The second is also a row that batch_id: None must skip. check_digit_for existed only for the decoy loop and is gone.

Test-only, so no CHANGELOG entry.

Verified: just check and just lint-integration green; t9 passes locally against Postgres 17 and fails with the identity index dropped.

[coderabbitai]

📝 Walkthrough

Walkthrough

The T9 identity-lookup integration test now uses two targeted decoys, disables sequential scans locally within a transaction, and requires the query plan to use idx_passport_identity. It removes the GTIN check-digit helper used to generate the former decoys.

Changes

Identity lookup test

Layer / File(s)	Summary
Identity lookup query-plan test crates/dpp-dal/tests/pg_integration.rs	The test replaces 200 generated decoys with two decoys that separately mismatch the target identifier and batch. It sets enable_seqscan = off within a transaction and requires the plan to name idx_passport_identity. It removes the GTIN check-digit helper.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other

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Merge Risk: 🔵 Low · up to b6cea

The test may miss a future query-plan regression in identity lookups. This is a bounded test-coverage gap; the PR otherwise appears mergeable.

Pre-merge checks · 6 · 1

Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check		The description gives detailed rationale, implementation changes, and verification results, but it does not follow the repository template. It omits the required section headings, related issue, bulle…	Restructure the description using the repository template. Add Summary, Related issue, Changes, and Checklist sections, and mark each checklist item with the applicable verification status.

Passed checks (6 passed)

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Publication Boundary		The reviewed diff changes only crates/dpp-dal/tests/pg_integration.rs. It adds test comments and SQL plan assertions, with no ADR reference, private repository name or path, commercial terms, or non…
New Dependency Is Justified		The pull request changes only crates/dpp-dal/tests/pg_integration.rs. It adds no direct dependency to any Cargo.toml, so the dependency justification requirement does not apply.
Title check		The title clearly and concisely identifies the main change: requiring the T9 test plan to use the identity index.

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Full details: Description check

Explanation

The description gives detailed rationale, implementation changes, and verification results, but it does not follow the repository template. It omits the required section headings, related issue, bullet-list changes, and checklist responses.

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Actionable comments posted: 1

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Inline comments:
Review comments at @crates/dpp-dal/tests/pg_integration.rs:
- Around line 746-748: Update the EXPLAIN query for find_by_identity to match
its complete lookup: include the serialNumber predicate and created_at ordering,
and remove LIMIT 1 so the planner evaluates the same query shape.

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