The feed's default `newest` sort is `published_at DESC NULLS LAST, id ASC`, but
the only published_at index was a plain ASC btree — read backwards it satisfies
DESC NULLS FIRST, not NULLS LAST — so every feed page fell back to a full
`videos` seq scan + top-N sort. Migration 0067 adds the two matching indexes
(global + per-channel) CONCURRENTLY and drops the now-redundant single-column
ix_videos_channel_id (the channel composite leads with channel_id, a strict
superset).
Measured on the prod-sized localdev reseed (257,312 videos, prod planner):
- global newest: 44,747 buffers / 154 ms -> 60 buffers / 0.32 ms
- per-channel(12.6k): 7,604 buffers / 96 ms -> 54 buffers / 0.14 ms
CONCURRENTLY build of both on 257k rows: 1.7s total (~0 downtime). This is the
likely root cause of the "prod feed is slow" symptom.
Model: drop the inline index=True on Video.channel_id (the composite supersedes
it); the composites are migration-defined like the search_vector GIN. Gate green
(334 pytest incl. the migration drift + downgrade/re-upgrade round-trip).
peter
3af3799b25