The fallback pulled artists only from explicit artist-likes (general_likes_artists),
but most users like albums and tracks far more than artists — so the artists row
still came up thin (a couple of tiles) even with a rich library, while the albums
row filled fine.
Broaden both fallbacks to "entities you've shown affinity for":
- artist fallback = explicit artist-likes ∪ artists of liked albums ∪ artists of
liked tracks.
- album fallback = explicit album-likes ∪ albums of liked tracks.
New dedicated queries (ListYouMightLike{Artist,Album}FallbackForUser) replace the
narrow Rediscover-fallback reuse; same projection so the Go layer still converts
directly. (Aliased + fully-qualified the UNION arms — sqlc merges UNION scopes,
so unqualified user_id was ambiguous across the three like tables.)
Test: 12 liked TRACKS by distinct artists, no artist-likes → the artist row now
fills from their artists (was empty before).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Surface in-library albums/artists the listener doesn't actively spin but
is predicted to enjoy, derived from the same similarity + like-weighted
candidate engine that powers For-You — rolled up from track scores to
album/artist granularity. Built in the daily 3am BuildSystemPlaylists
pass, atomic-replaced alongside the system playlists, and read back by
/api/home (+ /api/home/index).
Cold-start gate: skips generation entirely below 20 distinct unskipped
tracks AND 5 distinct artists, so a thin profile ships empty rows rather
than near-random tiles.
- migration 0034: you_might_like_albums / you_might_like_artists (id+rank,
CASCADE, per-user rank index).
- playlists/you_might_like.go: cold-start gate + similarity roll-up
(sum-of-top-3 aggregation, per-artist album cap, daily-rotating via the
same userIDHash jitter as For-You) + atomic-replace persist in the tx.
- recommendation/home.go: two new HomePayload sections with read-time
cross-section dedup vs Most Played / Rediscover / Last Played, trimmed
to 10 each.
- api: you_might_like_albums / you_might_like_artists on /api/home and
/api/home/index, reusing albumRefFrom / artistRefFromCovered.
- tests: pure roll-up/aggregation/cap unit tests + DB-backed gate,
sufficiency, and atomic-replace tests (all green vs real Postgres).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen