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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
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internal/db/dbq/recommendation.sql.go
+31 -15
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@@ -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 (