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fix(recommendation): artist-level arms take one track per related artist in turn (#5297)

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The similar_artists and coplay_artists arms ordered by artist score, so the
closest related artist's catalogue filled the whole LIMIT. On the operator's
library the 30-row similar_artists arm held exactly one artist for all 17
seeds measured (#3879), though each seed had 7-33 similar artists in the
library. Both arms now rank tracks within each artist and take every
artist's first track, best artist first, before anyone's second.

Both also skip missing tracks: the outer select already dropped them, but
only after they had taken places in the arm's LIMIT.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
bvandeusen
2026-10-07 19:56:21 -04:00
co-authored by Claude Opus 5.5
parent 865a3176c9
commit aa390c711a
3 changed files with 128 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files
internal/db/dbq/recommendation.sql.go
+31 -15
View File
@@ -828,13 +828,23 @@ lb_similar AS (
LIMIT $5
),
similar_artists AS (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'listenbrainz'
AND t.id NOT IN (SELECT id FROM excluded_ids)
ORDER BY asim.score DESC, md5(t.id::text || $12::text)
-- Round-robin across the similar artists (#5297): each artist's first
-- track, best-scoring artist first, then each one's second, and so on.
-- Ordering by artist score alone let the closest similar artist's
-- catalogue fill the whole LIMIT; on the operator's library this arm held
-- exactly one artist for all 17 seeds measured (#3879).
SELECT track_id, sim_score
FROM (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score, asim.score AS artist_score,
row_number() OVER (PARTITION BY asim.artist_b_id
ORDER BY md5(t.id::text || $12::text)) AS artist_turn
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id AND t.missing_since IS NULL
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'listenbrainz'
AND t.id NOT IN (SELECT id FROM excluded_ids)
) ranked
ORDER BY artist_turn, artist_score DESC, md5(track_id::text || $12::text)
LIMIT $6
),
tag_overlap AS (
@@ -882,14 +892,20 @@ coplay_artists AS (
-- the coplay worker). Mirrors similar_artists but from local co-occurrence
-- instead of ListenBrainz; empty on single-user servers. Same 0.5 damp as
-- similar_artists since it's artist-level.
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'user_cooccurrence'
AND t.id NOT IN (SELECT id FROM excluded_ids)
AND t.id <> $2
ORDER BY asim.score DESC, md5(t.id::text || $12::text)
-- Round-robin across artists for the same reason as similar_artists.
SELECT track_id, sim_score
FROM (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score, asim.score AS artist_score,
row_number() OVER (PARTITION BY asim.artist_b_id
ORDER BY md5(t.id::text || $12::text)) AS artist_turn
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id AND t.missing_since IS NULL
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'user_cooccurrence'
AND t.id NOT IN (SELECT id FROM excluded_ids)
AND t.id <> $2
) ranked
ORDER BY artist_turn, artist_score DESC, md5(track_id::text || $12::text)
LIMIT $11
),
random_fill AS (
internal/db/queries/recommendation.sql
+31 -15
View File
@@ -96,13 +96,23 @@ lb_similar AS (
LIMIT $5
),
similar_artists AS (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'listenbrainz'
AND t.id NOT IN (SELECT id FROM excluded_ids)
ORDER BY asim.score DESC, md5(t.id::text || $12::text)
-- Round-robin across the similar artists (#5297): each artist's first
-- track, best-scoring artist first, then each one's second, and so on.
-- Ordering by artist score alone let the closest similar artist's
-- catalogue fill the whole LIMIT; on the operator's library this arm held
-- exactly one artist for all 17 seeds measured (#3879).
SELECT track_id, sim_score
FROM (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score, asim.score AS artist_score,
row_number() OVER (PARTITION BY asim.artist_b_id
ORDER BY md5(t.id::text || $12::text)) AS artist_turn
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id AND t.missing_since IS NULL
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'listenbrainz'
AND t.id NOT IN (SELECT id FROM excluded_ids)
) ranked
ORDER BY artist_turn, artist_score DESC, md5(track_id::text || $12::text)
LIMIT $6
),
tag_overlap AS (
@@ -150,14 +160,20 @@ coplay_artists AS (
-- the coplay worker). Mirrors similar_artists but from local co-occurrence
-- instead of ListenBrainz; empty on single-user servers. Same 0.5 damp as
-- similar_artists since it's artist-level.
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'user_cooccurrence'
AND t.id NOT IN (SELECT id FROM excluded_ids)
AND t.id <> $2
ORDER BY asim.score DESC, md5(t.id::text || $12::text)
-- Round-robin across artists for the same reason as similar_artists.
SELECT track_id, sim_score
FROM (
SELECT t.id AS track_id, asim.score * 0.5 AS sim_score, asim.score AS artist_score,
row_number() OVER (PARTITION BY asim.artist_b_id
ORDER BY md5(t.id::text || $12::text)) AS artist_turn
FROM artist_similarity asim
JOIN tracks t ON t.artist_id = asim.artist_b_id AND t.missing_since IS NULL
JOIN seed_artist sa ON asim.artist_a_id = sa.artist_id
WHERE asim.source = 'user_cooccurrence'
AND t.id NOT IN (SELECT id FROM excluded_ids)
AND t.id <> $2
) ranked
ORDER BY artist_turn, artist_score DESC, md5(track_id::text || $12::text)
LIMIT $11
),
random_fill AS (
internal/recommendation/candidates_v2_test.go
+66
View File
@@ -429,3 +429,69 @@ func TestLoadCandidatesFromSimilarity_DifferentSeedsCanDrawDifferently(t *testin
"varying with the seed at all", len(seen))
}
}
// #5297: an artist-level arm takes a track from each related artist before a
// second from any. Ordered by artist score alone, the closest artist's
// catalogue filled the whole LIMIT; on the operator's library the
// similar_artists arm held one artist for every seed measured (#3879).
func TestLoadCandidatesFromSimilarity_ArtistArmsRoundRobin(t *testing.T) {
for _, source := range []string{"listenbrainz", "user_cooccurrence"} {
t.Run(source, func(t *testing.T) {
f := newFixture(t, 1)
ctx := context.Background()
seed := f.tracks[0]
artistOf := map[[16]byte]string{}
for i, score := range []float64{0.9, 0.8, 0.7} {
name := fmt.Sprintf("Related %d", i)
ar, err := f.q.UpsertArtist(ctx, dbq.UpsertArtistParams{Name: name, SortName: name})
if err != nil {
t.Fatal(err)
}
al, err := f.q.UpsertAlbum(ctx, dbq.UpsertAlbumParams{Title: name, SortTitle: name, ArtistID: ar.ID})
if err != nil {
t.Fatal(err)
}
// More tracks per artist than the arm's limit, so the closest
// artist alone could fill it.
for j := 0; j < 5; j++ {
tr, err := f.q.UpsertTrack(ctx, dbq.UpsertTrackParams{
Title: fmt.Sprintf("%s #%d", name, j), AlbumID: al.ID, ArtistID: ar.ID,
FilePath: fmt.Sprintf("/tmp/related-%d-%d.flac", i, j), DurationMs: 180_000,
})
if err != nil {
t.Fatal(err)
}
artistOf[tr.ID.Bytes] = name
}
if _, err := f.pool.Exec(ctx,
`INSERT INTO artist_similarity (artist_a_id, artist_b_id, score, source) VALUES ($1, $2, $3, $4)`,
seed.ArtistID, ar.ID, score, source); err != nil {
t.Fatal(err)
}
}
limits := CandidateSourceLimits{}
if source == "listenbrainz" {
limits.SimilarArtist = 3
} else {
limits.UserCoplay = 3
}
got, err := LoadCandidatesFromSimilarity(
ctx, f.q, f.user, seed.ID, 1, SessionVector{Seed: true}, nil, limits, "test-seed",
)
if err != nil {
t.Fatalf("load: %v", err)
}
artists := map[string]int{}
for _, c := range got {
if name, ok := artistOf[c.Track.ID.Bytes]; ok {
artists[name]++
}
}
if len(got) != 3 || len(artists) != 3 {
t.Errorf("arm of 3 drew %d candidates from %d related artists (%v), want one from each of 3",
len(got), len(artists), artists)
}
})
}
}