Milestone #127 step 2 (#1249). For You deliberately blends two
populations — a head of top-scored taste picks and a tail sampled from
deeper ranking (the freshness injection) — but the metrics judged it as
one blob, so its skip rate couldn't distinguish "the taste engine is
missing" from "the freshness tax is too high". That number decides the
exploration share before we tune it.
- Migration 0038: nullable pick_kind ('taste'|'fresh') on both
playlist_tracks (stamped at snapshot build) and play_events (frozen at
play-ingestion — the snapshot rebuilds daily, so attribution cannot be
reconstructed at read time).
- Builder: pickHeadAndTail marks head=taste / tail=fresh; the small-pool
fallback is all taste (top-N-by-score IS the taste mechanism). Other
variants persist NULL.
- Ingestion: for_you plays (live + offline replay) look the track up in
the user's current snapshot; not found → unattributed, never guessed.
- Metrics: For You's row gains a breakdown (taste / fresh / earlier
unattributed plays), parent row stays the sum; web card renders the
sub-rows indented with the same baseline deltas + low-data dimming.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
Returns batched upserts + deletes since the supplied cursor. Empty cursor
returns full snapshot; subsequent calls pull deltas. Per-user entities
(likes, playlists) are scoped to the authed user. Composite-key entities
(likes, playlist_tracks) use stable string ids encoded by sync.EncodeLikeID
/ sync.EncodePlaylistTrackID.
Behavior:
204 No Content - no changes since cursor
200 OK - JSON syncResponse {cursor, upserts, deletes}
410 Gone - cursor older than oldest log row; client must reset
401 / 500 - standard envelope errors
Adds sqlc queries GetAlbumsByIDs, GetTracksByIDs, GetPlaylistsByIDs to
mirror the existing GetArtistsByIDs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Migration 0014 adds playlists + playlist_tracks. track_id is nullable
with ON DELETE SET NULL — tracks can be removed from the library
without silently dropping playlist entries; the denormalized snapshot
(title/artist/album/duration) keeps the row legible afterwards. UI
renders such rows greyed-out.
Indexes: playlists by (user_id, updated_at DESC) and a partial public
index for cross-user discovery; playlist_tracks partial index on
track_id to support the FK SET NULL lookup.
Queries provide CRUD + rollup recompute (track_count, duration_sec)
+ append/remove primitives. Reorder is service-layer orchestrated via
raw tx.Exec; no SQL primitive needed.
bvandeusen