handleGetHome itself is well-architected (5 sections in parallel via
goroutines, latency-bound by the slowest single query). The cold-
start lag is two of those queries doing wider scans than necessary.
ListLastPlayedArtistsForUser was iterating FROM artists a with a
LATERAL play_events join per row — O(total_artists in library) plan
even for users who've only played a handful. Inverted: aggregate the
user's plays by artist_id first via the play_events → tracks join
(uses play_events_user_track_idx + tracks pkey), then attach the
artist row and lateral cover/count subqueries only for the artists
that actually appear. Cost now bounded by play history, not library
size.
ListMostPlayedTracksForUser was joining tracks/albums/artists for
every play_event row before grouping — O(total plays) work for
joins. Pre-aggregated play_events into a CTE keyed by track_id +
count(*), then joined to tracks/albums/artists only for the
distinct-tracks survivors. Order-by uses the pre-computed count.
No handler or generated-Go signature changes — both queries return
the same rowset shape, just much faster on libraries where total
artists/plays >> distinct-played-artists/distinct-played-tracks.
Add per-user artist-suggestion service ranking out-of-library MBIDs by
signal x similarity. Single-CTE SQL collects user likes (5x weight) and
recency-decayed plays, joins against artist_similarity_unmatched, and
filters in-library candidates plus non-terminal lidarr_requests. The
service resolves top-3 attribution seeds to artist names in a batched
GetArtistsByIDs call so the UI can render "because you liked X" reasons.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The combined seed_info CTE filtered the seed out when its genre was
NULL/empty. Restored the spec's two-CTE design (seed_artist + seed_tags)
so similar-artist matching works regardless of the seed's genre coverage.
Drops the genre workaround from the SimilarArtist test.
Single SELECT that joins tracks with general_likes (for is_liked) and
an aggregated LATERAL subquery on play_events (for last_played_at,
play_count, skip_count). Excludes seed + tracks played in the last
N hours. Drives the M3 weighted shuffle scoring.
bvandeusen