Eric Allam
4c58091973
## Why this change Deleting a `ProjectAlertChannel` fires the FK cascade `DELETE FROM ONLY "ProjectAlert" WHERE $1 = "channelId"`. That cascade is scan-shaped: with no index on `channelId`, it reads the entire `ProjectAlert` table to find the few child rows belonging to the deleted channel. The parent `DELETE ProjectAlertChannel` does almost no work itself; its latency is dominated by this cascade. `ProjectAlert` is append-heavy and grows over time, so the scan cost only increases. ## Diagnosis `ProjectAlert` had no index on `channelId` (only `pkey` + a `friendlyId` unique). The cascade therefore did a full sequential scan of the whole table. The sibling `ProjectAlertStorage` cascade on the same delete is index-backed and stays fast, which isolates the missing index as the cause. ## Change Add `@@index([channelId])` on `ProjectAlert`, created with `CREATE INDEX CONCURRENTLY IF NOT EXISTS` so `prisma migrate deploy` stays safe on a live table. ## Benchmark (local, seeded) Local Postgres seeded with 1,000,000 `ProjectAlert` rows across 50 channels (~20k rows per channel), `EXPLAIN (ANALYZE, BUFFERS)` on the cascade delete: | | before | after | |---|---|---| | plan | Seq Scan (1M rows) | Bitmap Index Scan | | direct child delete | 740 ms | 22 ms | | parent delete `ProjectAlert_channelId_fkey` trigger | 77.7 ms | 23.8 ms | ## Expected impact The cascade drops from a full-table sequential scan to a targeted index lookup. The win grows with the table: the more rows in `ProjectAlert`, the more a scan costs and the more the index saves, so the benefit is larger than the seeded numbers above. ## Risks - One extra btree to maintain on every `ProjectAlert` insert; acceptable for a single-column index on a high-insert table, and it should be pre-created before the migration deploys (per the repo index rules). - No behavior change: no rows orphaned, no ordering or result-set change, read paths untouched. ## Follow-up `ProjectAlert`'s other cascade FK columns (`projectId`, `environmentId`, `workerDeploymentId`) are also unindexed, but their parents are soft-deleted rather than physically removed, so those cascades do not currently fire. Lower priority unless a hard-delete path is introduced.
@trigger.dev/database
This is the internal database package for the Trigger.dev project. It exports a generated prisma client that can be instantiated with a connection string.
How to switch branches when you've done migrations
Sometimes you've applied migrations and then want to switch branches without wiping out your local database.
To do this you can run the following command:
DB_VOLUME=database-data-alt pnpm run docker
This will switch to the alt volume for your local database. This database will be blank if you haven't switched to this volume before, so you'll need to follow the normal steps (in the Contributing guide) to get setup, e.g. apply migrations and seed.
To switch back to the original volume, run the following command:
pnpm run docker
How to add a new index on a large table
- Modify the Prisma.schema with a single index change (no other changes, just one index at a time)
- Create a Prisma migration using
cd internal-packages/database && pnpm run db:migrate:dev:create - Modify the SQL file: add IF NOT EXISTS to it and CONCURRENTLY:
CREATE INDEX CONCURRENTLY IF NOT EXISTS "JobRun_eventId_idx" ON "JobRun" ("eventId");
- Don’t apply the Prisma migration locally yet. This is a good opportunity to test the flow.
- Manually apply the index to your database, by running the index command.
- Then locally run
pnpm run db:migrate:deploy
Before deploying
Run the index creation before deploying
CREATE INDEX CONCURRENTLY IF NOT EXISTS "JobRun_eventId_idx" ON "JobRun" ("eventId");
These commands are useful:
-- creates an index safely, this can take a long time (2 mins maybe)
CREATE INDEX CONCURRENTLY IF NOT EXISTS "JobRun_eventId_idx" ON "JobRun" ("eventId");
-- checks the status of an index
SELECT * FROM pg_stat_progress_create_index WHERE relid = '"JobRun"'::regclass;
-- checks if the index is there
SELECT * FROM pg_indexes WHERE tablename = 'JobRun' AND indexname = 'JobRun_eventId_idx';
Now, when you deploy and prisma runs the migration, it will skip the index creation because it already exists. If you don't do this, there will be pain.