[Perf] Cap my_follows CTE at 200 in GetTracks/GetPlaylists#793
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raymondjacobson merged 1 commit intomainfrom May 8, 2026
Merged
[Perf] Cap my_follows CTE at 200 in GetTracks/GetPlaylists#793raymondjacobson merged 1 commit intomainfrom
raymondjacobson merged 1 commit intomainfrom
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The CTE feeds two consumers (followee_reposts, followee_favorites) that each emit at most 3 rows ordered by follower_count DESC. The existing LIMIT 5000 was non-binding for nearly every user and materialized far more rows than the LATERAL ever needs. Verified on the prod read replica with user 20 (1752 follows) and a 10-track id list, three warm runs each (PR 1 MATERIALIZED applied): LIMIT 5000: 86, 97, 92 ms (mean 92) LIMIT 200: 43, 31, 23 ms (mean 32) ~2.9x Edge case: a user whose only follower-of-X is ranked >200 by their own follower_count will no longer surface in followee_*. Acceptable trade-off: those low-fanout reposts are dominated by the top-200 in the social-proof rendering anyway.
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Summary
Lower
LIMIT 5000toLIMIT 200in themy_followsCTE used byGetTracksandGetPlaylists. The CTE feeds two consumers (followee_reposts,followee_favorites) that each emit at most 3 rows ordered byfollower_count DESC, so 5000 was almost always materializing more than the LATERAL ever consumed.Impact
Verified on the prod read replica with user 20 (1752 follows), 10-track id list, three warm runs each (with #792 /
MATERIALIZEDapplied):Stacks with #792.
GetTracksandGetPlayliststogether represent ~310M calls / 4.5B ms inpg_stat_statements.Risk
follower_countwill no longer surface infollowee_reposts/followee_favorites. Acceptable trade-off — those low-fanout reposts are already dominated by the top-200 in the rendered top-3 social proof.TestGetTrackPersonalization(added in [Perf] MATERIALIZE my_follows CTE in GetTracks/GetPlaylists #792) and the rest of the suite cover the personalization shape.Test plan
go test -count=1 ./api/...(full suite, all green)/v1/tracks/trending?user_id=Wem1e(Phuture, 1752 follows) — 400-600ms warmStacks on
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