Twenty-one foreign keys with ON DELETE CASCADE or SET NULL had no index
leading with their column, so deleting a parent scanned the child table
once per row; medication_intake_events.medication_id was the one an
account delete paid for. Seventeen small-table indexes and the measurements
(user_id, type, measured_at) index repeated the leading columns of another
index and only cost writes.
Migration 0415 adds and drops the small-table ones in one DO block under a
bounded lock wait; 0416 drops the measurements index concurrently, in a
file of its own. An integration test holds the schema to both rules from
the catalog, each with a counter-check, and compares the plans of the
user-and-type query shapes on a seeded table with and without the dropped
index. The lock-timeout guard now also requires a CONCURRENTLY statement
to stand alone in its file.
migrate deploy runs a migration file statement by statement, so the
top-level SET LOCAL lock_timeout in 0412 did nothing: the migration
waited as long as the lock was held, with every write to measurements
queued behind it, and a file that failed half-way stayed half-applied.
0412 now takes its locks inside one DO block with a statement-scoped
timeout, which rolls back whole, after an idempotent CREATE OR REPLACE.
The entrypoint runs migrate deploy through scripts/migrate-deploy.mjs.
A 55P03 failure of a migration marked -- @retry-on-lock-timeout is
marked rolled back and retried after 15/30/60/120/240 s, read from
Prisma's report or, after P3009, from the stored row. Every other
failure stays fatal. A guard holds migrations to the shape that makes
the marker true, and 0411/0413 add their columns with IF NOT EXISTS so
a manual re-run is safe too.
Marc-André Bombeck