perf(db): index playlist trending order#906
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raymondjacobson
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Jun 8, 2026
## Summary - clamps the For You recency-decay exponent before calling `exp(...)` - keeps very old candidates ranked as effectively zero-recency instead of returning a 500 - adds a regression test with a year-1900 trending candidate ## Production evidence - during the #905/#906 release watch, `/v1/users/:userId/feed/for-you` returned 500s with `SQLSTATE 22003` underflow for several users - a read-only prod probe reproduced the raw failure with `exp((-1000000)::double precision)` - the exact clamped expression against a year-1900 timestamp returned a finite `9.85967654375977e-305` score ## Verification - `go test ./api -run 'TestV1FeedForYou' -count=1 -timeout=3m`\n- `git diff --check`
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Summary
playlist_trending_scores(type, version, time_range, score DESC, playlist_id DESC)/v1/playlists/trendingand For You playlist candidate sources without changing API behaviorProduction evidence
ORDER BY score DESC, playlist_id DESC LIMIT ...patternidx_playlist_trending_scores_filteredputsplaylist_idbeforescore, which cannot satisfy the requested orderingtype,version, andtime_range, then page by score/tie-breaker; this index follows that shape directlyVerification
CREATE INDEX CONCURRENTLY IF NOT EXISTSplus an index comment