compute_semantic_links_ann created a TEMP TABLE outside any transaction,
then ran a TRUNCATE / COPY / SELECT / DROP sequence as separate statements
on the same asyncpg connection. This is fine against a direct Postgres
connection but fails intermittently when the caller is routed through
PgBouncer in transaction pool mode:
CREATE TEMP TABLE IF NOT EXISTS _ann_seeds (...) -- backend A
TRUNCATE _ann_seeds -- backend B -> FAILS
Temp tables are session-scoped to the backend that created them. In
PgBouncer transaction mode the backend is only pinned to the client for
the duration of an actual transaction, so between standalone statements
the pooler can (and under concurrency, will) rebind the client to a
different backend. When that happens the _ann_seeds table disappears
and the follow-up statement fails with:
relation "_ann_seeds" does not exist
Symptom: ~3% of sync retain calls (2 of 61) failed the Hindsight Cloud
smoke test on a recent hindsight-dev deploy. Async retains are masked
by the 3-attempt retry loop so they usually eventually succeed.
Fix: wrap the CREATE TEMP TABLE -> COPY -> SELECT sequence in a single
`async with conn.transaction():` block, and use ON COMMIT DROP so the
temp table is transaction-scoped and auto-cleaned at commit. Also
switch `SET hnsw.ef_search = 60` to `SET LOCAL` so the tuning is
transaction-scoped and no longer leaks onto the pooled backend for
subsequent recall queries. Drop the now-unnecessary manual TRUNCATE,
explicit DROP TABLE, and RESET hnsw.ef_search.
The function docstring still correctly describes this as running on a
separate connection outside the surrounding write transaction — this
change only adds an inner transaction around the ANN work itself to
keep the temp table visible to PgBouncer.
Tests:
- Add TestComputeSemanticLinksAnnPgBouncerSafety with 5 regression
tests using a mocked connection. These are structural asserts — they
check that the function enters conn.transaction(), uses ON COMMIT DROP,
uses SET LOCAL, and does not reintroduce manual TRUNCATE / DROP /
RESET calls. They would have caught the original bug if they had
existed, and will catch any future reversion.
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