set a temporary album tag artist for those who mightn't have it yet

db/migrations.go

@@ -70,6 +70,7 @@ func (db *DB) Migrate(ctx MigrationContext) error {
 		construct(ctx, "202310281803", migrateTrackArtists),
 		construct(ctx, "202311062259", migrateArtistAppearances),
 		construct(ctx, "202311072309", migrateAlbumInfo),
+		construct(ctx, "202311082304", migrateTemporaryDisplayAlbumArtist),
 	}
 
 	return gormigrate.
@@ -787,3 +788,17 @@ func migrateAlbumInfo(tx *gorm.DB, _ MigrationContext) error {
 	).
 		Error
 }
+
+func migrateTemporaryDisplayAlbumArtist(tx *gorm.DB, _ MigrationContext) error {
+	// keep some things working so that people have an album.tag_artist_id until their next full scan
+	return tx.Exec(`
+		UPDATE albums
+		SET tag_album_artist=(
+			SELECT group_concat(artists.name, ', ')
+			FROM artists
+			JOIN album_artists ON album_artists.artist_id=artists.id AND album_artists.album_id=albums.id
+			GROUP BY album_artists.album_id
+		)
+		WHERE tag_album_artist=''
+	`).Error
+}

server/ctrlsubsonic/handlers_common.go

@@ -7,8 +7,6 @@ import (
 	"math"
 	"net/http"
 	"path/filepath"
-	"sort"
-	"strings"
 	"sync"
 	"time"
 	"unicode"
@@ -72,7 +70,7 @@ func (c *Controller) ServeScrobble(r *http.Request) *spec.Response {
 		scrobbleTrack.Track = track.TagTitle
 		scrobbleTrack.Artist = track.TagTrackArtist
 		scrobbleTrack.Album = track.Album.TagTitle
-		scrobbleTrack.AlbumArtist = albumArtistString(track.Album)
+		scrobbleTrack.AlbumArtist = track.Album.TagAlbumArtist
 		scrobbleTrack.TrackNumber = uint(track.TagTrackNumber)
 		scrobbleTrack.Duration = time.Second * time.Duration(track.Length)
 		if _, err := uuid.Parse(track.TagBrainzID); err == nil {
@@ -517,21 +515,3 @@ func lowerUDecOrHash(in string) string {
 	}
 	return string(lower)
 }
-
-// not everyone's records may have the album.TagAlbumArtist column set, since we didn't always store that.
-// try it first, but fallback to a list from the artists table
-func albumArtistString(album *db.Album) string {
-	if album.TagAlbumArtist != "" {
-		return album.TagAlbumArtist
-	}
-
-	artists := append([]*db.Artist(nil), album.Artists...)
-	sort.Slice(artists, func(i, j int) bool {
-		return artists[i].ID < artists[j].ID
-	})
-	names := make([]string, 0, len(artists))
-	for _, artist := range artists {
-		names = append(names, artist.Name)
-	}
-	return strings.Join(names, ", ")
-}