perf: index the promoted-property search

[hamzahalq]

The property filter is the slowest thing on the Exchanges page and, per the client, the most used. On their production data (850,984 exchanges) picking a promoted key from the dropdown takes 29.3 seconds.

Why

The search is a substring match, so it reaches SQL as:

WHERE LOWER(properties_raw) LIKE '%first time:%'

A leading wildcard has no fixed prefix to look up, so the b-tree that already exists on that column can never serve it — every search reads the entire table. That index has in fact never been usable for this query.

The change

A trigram (pg_trgm) GIN index on lower(properties_raw). Trigram indexes index three-character sequences, which is what allows a wildcard-on-both-sides LIKE to use an index at all.

Postgres-only, so it lives in the PgSql provider as raw SQL and leaves the shared model untouched — MigrationDriftTests passes on all three providers.

Measured

On a throwaway database seeded with 1,000,000 exchanges, through the real API:

filter	before	after
property key only	6,234 ms	228 ms
— rows query	4,845 ms	4 ms
— count query	1,359 ms	217 ms
property key + value	2,488 ms	161 ms
a rare property value	—	25 ms

Cost

83 MB against a 411 MB table on the million-row copy (~20%), and it's written on every new exchange. That's the trade for a search that is otherwise unusable at this volume.

Deploying this

Built with CREATE INDEX CONCURRENTLY. A plain build takes an ACCESS EXCLUSIVE lock for its whole duration — ~6s per million rows locally, longer on a managed instance — and every exchange the engine processes writes a row to this table, so a plain build would stall processing. CONCURRENTLY can't run inside a transaction, hence suppressTransaction: true; the generated script correctly puts it outside the transaction that creates the extension.

One thing to know: if a CONCURRENTLY build fails part-way it leaves an INVALID index behind rather than nothing. The IF NOT EXISTS makes a retry safe rather than a hard error, but an invalid index should be dropped and rebuilt rather than left in place.

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SW.Bitween.PgSql/Migrations/20260901121718_PromotedPropertiesTrigramIndex.cs (1)

22-23: LGTM!

Also applies to: 43-47, 49-66, 68-72, 74-81, 87-89

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📝 Walkthrough

What changed

• Added EF Core migration PromotedPropertiesTrigramIndex.
• Enabled pg_trgm.
• Added a concurrent GIN index on lower(properties_raw) for promoted-property substring searches.
• Added repair handling for invalid indexes and runs ANALYZE after index creation.
• Left the shared model and MsSql/MySql providers unchanged.

Risk

risk:medium

Security-sensitive areas

• The migration executes raw PostgreSQL SQL.
• The migration requires permission to install pg_trgm and create indexes.
• No authentication, authorization, or application data-handling logic changed.

Test coverage impact

• No automated test changes are reported.
• Drift tests pass for all three providers.
• Migration application was re-verified from scratch and on a second run.
• Performance improved on 1 million exchanges, with warm key searches near 257 ms and rare-value searches near 16 ms.

Deployment and operational concerns

• CREATE INDEX CONCURRENTLY requires transaction suppression.
• Monitor index creation time and database load during deployment.
• If a concurrent build fails, the migration drops the invalid index before rebuilding it.
• ANALYZE is required for effective planner statistics on the expression index.
• Rollback drops the index concurrently but leaves the pg_trgm extension installed.

Walkthrough

Adds an EF Core migration and generated model snapshot. The migration enables pg_trgm, repairs invalid leftover indexes, and creates a concurrent GIN index on lower(properties_raw) for infolink.xchange_promoted_properties. Downgrade removes the index.

Changes

Promoted properties search index

Layer / File(s)	Summary
Migration model snapshot SW.Bitween.PgSql/Migrations/20260901121718_PromotedPropertiesTrigramIndex.Designer.cs	Adds the generated BitweenDbContext model metadata for domain and Quartz entities, including properties, keys, indexes, seed data, owned types, relationships, and navigations.
Concurrent trigram index operations SW.Bitween.PgSql/Migrations/20260901121718_PromotedPropertiesTrigramIndex.cs	Creates the pg_trgm extension, removes invalid leftover indexes, creates the concurrent GIN index on lower(properties_raw), analyzes the table, and drops the index concurrently during downgrade.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to 3c329

The PostgreSQL migration adds a trigram index to substantially speed promoted-property searches, but concurrent deployment runners could interfere with index cleanup or creation and interrupt rollout. Confirm serialized migration execution or use ownership-safe cleanup before deployment; application behavior and security exposure are otherwise unchanged.

Suggested labels: database, risk:high

Suggested reviewers: ahmadrabuhussein

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding an index to improve promoted-property search performance.
Description check	✅ Passed	The description directly explains the slow substring search, the PostgreSQL trigram index, measured performance gains, deployment behavior, and operational trade-offs.
Docstring Coverage	✅ Passed	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 3 functions across 2 files.
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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[hamzahalq]

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Inline comments:
In
`@SW.Bitween.PgSql/Migrations/20260901121718_PromotedPropertiesTrigramIndex.cs`:
- Around line 40-42: Update the migration’s promoted-properties trigram index
creation around ix_xchange_promoted_properties_properties_raw_trgm to detect an
existing invalid index and repair or rebuild it before the CREATE INDEX
CONCURRENTLY retry; do not let IF NOT EXISTS skip an invalid index, and preserve
the intended valid GIN trigram index on lower(properties_raw).

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SW.Bitween.PgSql/Migrations/20260901121718_PromotedPropertiesTrigramIndex.Designer.cs

[high] 123-123: Detected a potential hardcoded password literal, which may expose account credentials.

(generic-password)

---

[high] 2205-2205: Detected a Generic API Key, potentially exposing access to various services and sensitive operations.

(generic-api-key)

[hamzahalq]

Pushed two fixes to the migration.

1. Repair a broken index before building — the finding above. Tested by marking the index indisvalid = false, re-running the migration, and confirming it drops and rebuilds rather than skipping. A plain DROP rather than CONCURRENTLY, since the latter can't run inside a DO block and an invalid index holds no data.

2. ANALYZE after building — found while verifying, and the more dangerous of the two. Postgres only gathers statistics for an index on an expression when ANALYZE runs, so until then the planner has no selectivity estimate for lower(properties_raw) LIKE … and picks a worse plan than having no index:

property-key filter, 1M exchanges	time
no index (production today)	8,103 ms
index, no statistics	19,437 ms
index + statistics	257 ms

The original numbers in this PR were measured with a manual ANALYZE that the migration didn't perform, so as it stood this could have shipped a regression.

Re-verified, applying the migration from scratch on the 1M-row copy: property key only 8,103 → 795 ms, key + value 810 → 272 ms, a rare value 201 → 16 ms. The 795 ms is the first request after the build; it settles to ~257 ms warm. Applied twice — idempotent. Drift tests pass on all three providers.

On doing this through the model instead (raised in review): the model-declarable form is a trigram index on the bare column matched with ILIKE, which I measured and it does work. But it needs EF.Functions.ILike at the call site, and Xchanges/Search.cs lives in SW.Bitween.Api, which references only EntityFrameworkCore.Relational and no provider by design. Adding Npgsql there to reach a Postgres function seemed worse than one raw-SQL migration inside the Postgres-only project. The reasoning is in the file.

MsSql and MySql are untouched and stay as they are — there is no portable index for substring-anywhere matching, and the alternatives (full-text) match whole words, which would give each database different search behaviour.