perf: declare fetch partial index inside make_outbox_table#3
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The fetch query's hot branch (`WHERE acquired_token IS NULL AND queue = ?
AND next_attempt_at <= now()`) needs a composite partial index to avoid a
sequential scan. Until now this was a recommendation in the README that
users had to add to their Alembic migration manually — easy to forget,
silently catastrophic for throughput.
Declare the index on the Table itself so Alembic autogenerate brings it
up alongside the table:
CREATE INDEX outbox_pending_idx ON outbox (queue, next_attempt_at)
WHERE acquired_token IS NULL;
Drop the now-redundant standalone indexes:
- `queue` (`index=True` on the column) — covered by the composite.
- `outbox_next_attempt_at_idx` — same.
Lease-expired rows fall back to a sequential scan when fetch reclaims
them; that's fine because expired leases are rare.
The partial index is declared inside make_outbox_table and brought up by Alembic autogenerate — users don't need to know it exists.
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The fetch query's hot branch (
WHERE acquired_token IS NULL AND queue = ? AND next_attempt_at <= now()) needs a composite partial index to avoid a sequential scan. Until now this was a recommendation in the README that users had to add to their Alembic migration manually — easy to forget, silently catastrophic for throughput.Declare the index on the Table itself so Alembic autogenerate brings it up alongside the table:
Drop the now-redundant standalone indexes:
queue(index=Trueon the column) — covered by the composite.outbox_next_attempt_at_idx— same.Lease-expired rows fall back to a sequential scan when fetch reclaims them; that's fine because expired leases are rare.