fix(api): stop profile/dashboard track queries from seq-scanning tracks (perf regression from #932)#942
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#932 folded accepted-collaborator tracks into GET /users/:id/tracks (and the dashboard monthly-listens query) as `OR t.track_id IN (SELECT ... FROM track_collaborators ...)`. That OR across two access paths defeats the tracks(owner_id) index, so Postgres sequential-scanned the entire tracks table on every profile load — a severe regression on a top-QPS endpoint. Fix: fetch the user's accepted-collaboration track ids first (a tiny index-only lookup that returns nothing for ~all users), and only widen the query when the set is non-empty — via an explicit `= ANY($ids)` array (bitmap-OR of the owner_id index and the track_id PK), not a correlated subquery. For users with no collaborations the query is byte-identical to the pre-#932 owner-only query and plan. Same treatment for v1_users_listen_counts_monthly. Behavior is unchanged (tests for the merge, pending-hidden, and the no-collab path all pass). Co-Authored-By: Claude Opus 4.8 <[email protected]>
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Incident hotfix
After #932 deployed,
GET /users/:id/tracks(and the dashboard monthly-listens query) started sequential-scanning the entiretrackstable on every request, melting the DB on a top-QPS endpoint.Root cause
#932 merged accepted-collaborator tracks into the profile query as:
That
ORacross two different access paths (an indexed column ontracksvs. a semi-join subquery) defeats thetracks(owner_id)index. With the subquery's poor row estimate, the planner falls back to a seq scan oftracks(+ theaggregate_*joins, then sort) — per request. Not feature-gated, so it hit 100% of profile loads immediately, despite zero collaborations existing yet (frontend isn't out).Fix
Fetch the user's accepted-collaboration track ids first — a tiny index-only lookup on the covering
(collaborator_user_id, status, track_id)index that returns nothing for ~every user — then:t.track_id = ANY($ids)array, which the planner handles with a bitmap OR of theowner_idindex and thetrack_idPK — not a correlated subquery.Same treatment applied to
v1_users_listen_counts_monthly.Correctness
Behavior is unchanged. Passing:
TestGetUserTracks(no-collab path),TestAcceptedCollaborationAppearsOnProfile(merge still works),TestPendingCollaborationHiddenFromProfile,TestV1UsersListenCountsMonthly, the collaborator embed/notification tests.Note
This is the perf risk I'd flagged in the #932 review (the
OR … INpattern). If you need relief before this merges, reverting justv1_users_tracks.go+v1_users_listen_counts_monthly.goto their pre-#932 owner-only queries is a zero-risk instant mitigation — there are no real collaborations yet, so nothing is lost.🤖 Generated with Claude Code