normalize every song's genres into song_genres and simplify the genre queries

app/src/main/kotlin/com/subtracks/data/db/LibraryDao.kt

@@ -305,16 +305,10 @@ interface LibraryDao {
     ): Flow<List<AlbumSongItem>>
 
     @Query(
-        "SELECT genre FROM (" +
+        "SELECT song_genres.genre FROM song_genres " +
-            "SELECT song_genres.genre AS genre, songs.playCount AS plays FROM song_genres " +
             "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
             "WHERE song_genres.sourceId = :sourceId " +
-            "UNION ALL " +
+            "GROUP BY song_genres.genre ORDER BY SUM(songs.playCount) DESC, song_genres.genre COLLATE NOCASE",
-            "SELECT songs.genre AS genre, songs.playCount AS plays FROM songs " +
-            "WHERE songs.sourceId = :sourceId AND songs.genre IS NOT NULL AND songs.genre != '' " +
-            "AND NOT EXISTS (SELECT 1 FROM song_genres " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id)" +
-            ") GROUP BY genre ORDER BY SUM(plays) DESC, genre COLLATE NOCASE",
     )
     fun genresByMostPlayed(sourceId: Long): Flow<List<String>>
 
@@ -737,14 +731,10 @@ interface LibraryDao {
     fun homeDownloadedSongs(sourceId: Long): PagingSource<Int, AlbumSongItem>
 
     @Query(
-        "SELECT songs.*, albums.coverArt AS coverArt FROM songs " +
+        "SELECT songs.*, albums.coverArt AS coverArt FROM song_genres " +
+            "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
             "LEFT JOIN albums ON albums.sourceId = songs.sourceId AND albums.id = songs.albumId " +
-            "WHERE songs.sourceId = :sourceId AND (" +
+            "WHERE song_genres.sourceId = :sourceId AND song_genres.genre = :genre " +
-            "EXISTS (SELECT 1 FROM song_genres " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id " +
-            "AND song_genres.genre = :genre) " +
-            "OR (songs.genre = :genre AND NOT EXISTS (SELECT 1 FROM song_genres " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id))) " +
             "ORDER BY songs.title COLLATE NOCASE, songs.id",
     )
     fun songsByGenre(
@@ -753,13 +743,9 @@ interface LibraryDao {
     ): PagingSource<Int, AlbumSongItem>
 
     @Query(
-        "SELECT songs.id FROM songs " +
+        "SELECT songs.id FROM song_genres " +
-            "WHERE songs.sourceId = :sourceId AND (" +
+            "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
-            "EXISTS (SELECT 1 FROM song_genres " +
+            "WHERE song_genres.sourceId = :sourceId AND song_genres.genre = :genre " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id " +
-            "AND song_genres.genre = :genre) " +
-            "OR (songs.genre = :genre AND NOT EXISTS (SELECT 1 FROM song_genres " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id))) " +
             "ORDER BY songs.title COLLATE NOCASE, songs.id",
     )
     suspend fun songsByGenreIds(
@@ -826,16 +812,10 @@ interface LibraryDao {
     ): Flow<List<String>>
 
     @Query(
-        "SELECT genre FROM (" +
+        "SELECT DISTINCT song_genres.genre FROM song_genres " +
-            "SELECT song_genres.genre AS genre FROM song_genres " +
             "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
             "WHERE songs.sourceId = :sourceId AND songs.albumId = :albumId " +
-            "UNION " +
+            "ORDER BY song_genres.genre COLLATE NOCASE",
-            "SELECT songs.genre AS genre FROM songs " +
-            "WHERE songs.sourceId = :sourceId AND songs.albumId = :albumId AND songs.genre IS NOT NULL " +
-            "AND NOT EXISTS (SELECT 1 FROM song_genres " +
-            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id)" +
-            ") ORDER BY genre COLLATE NOCASE",
     )
     fun albumGenres(
         sourceId: Long,

app/src/main/kotlin/com/subtracks/data/db/Migrations.kt

@@ -339,6 +339,19 @@ val MIGRATION_22_23 =
         }
     }
 
+val MIGRATION_23_24 =
+    object : Migration(23, 24) {
+        override suspend fun migrate(connection: SQLiteConnection) {
+            connection.execSQL(
+                "INSERT INTO `song_genres` (`sourceId`, `songId`, `position`, `genre`) " +
+                    "SELECT `sourceId`, `id`, 0, `genre` FROM `songs` " +
+                    "WHERE `genre` IS NOT NULL AND `genre` != '' " +
+                    "AND NOT EXISTS (SELECT 1 FROM `song_genres` sg " +
+                    "WHERE sg.`sourceId` = `songs`.`sourceId` AND sg.`songId` = `songs`.`id`)",
+            )
+        }
+    }
+
 // Mirrors the FTS5 table and content-sync triggers Room generates for the @Fts5 entities.
 private suspend fun createSearchIndex(
     connection: SQLiteConnection,
@@ -395,4 +408,5 @@ val MIGRATIONS: Array<Migration> =
         MIGRATION_20_21,
         MIGRATION_21_22,
         MIGRATION_22_23,
+        MIGRATION_23_24,
     )

app/src/main/kotlin/com/subtracks/data/db/SubtracksDatabase.kt

@@ -45,7 +45,7 @@ import com.subtracks.data.model.UpNextEntry
         ArtworkSeed::class,
         SongDownload::class,
     ],
-    version = 23,
+    version = 24,
     exportSchema = true,
 )
 @ColumnTypeConverters(QueueKindConverter::class, DownloadStatusConverter::class)

app/src/main/kotlin/com/subtracks/data/sync/SyncService.kt

@@ -72,9 +72,10 @@ class SyncService(
     }
 
     private suspend fun writeSongs(batch: List<Song>) {
+        val names = batch.associate { it.id to it.genreNames() }
         val genres =
             batch.flatMap { song ->
-                song.genres.mapIndexed { index, genre -> SongGenre(song.sourceId, song.id, index.toLong(), genre) }
+                names.getValue(song.id).mapIndexed { index, genre -> SongGenre(song.sourceId, song.id, index.toLong(), genre) }
             }
         db.useWriterConnection { connection ->
             connection.immediateTransaction {
@@ -83,7 +84,7 @@ class SyncService(
                     batch.forEach { song ->
                         statement.bind(1, song.sourceId)
                         statement.bind(2, song.id)
-                        statement.bind(3, song.genres.size.toLong())
+                        statement.bind(3, names.getValue(song.id).size.toLong())
                         statement.step()
                         statement.reset()
                         statement.clearBindings()
@@ -284,6 +285,8 @@ private val songColumns =
 
 private val playlistColumns = listOf("sourceId", "id", "name", "comment", "coverArt", "songCount", "created", "changed", "duration")
 
+private fun Song.genreNames(): List<String> = genres.ifEmpty { listOfNotNull(genre?.trim()?.takeIf { it.isNotEmpty() }) }
+
 private val songGenreColumns = listOf("sourceId", "songId", "position", "genre")
 
 private val songGenreKey = listOf("sourceId", "songId", "position")

app/src/test/kotlin/com/subtracks/data/db/LibraryHomeDaoTest.kt

@@ -132,12 +132,16 @@ class LibraryHomeDaoTest {
             val dao = db.libraryDao()
             dao.upsertSongs(
                 listOf(
-                    song(sourceId, "s1", "One", genre = "Rock", playCount = 5),
+                    song(sourceId, "s1", "One", playCount = 5),
-                    song(sourceId, "s2", "Two", genre = "Jazz", playCount = 2),
+                    song(sourceId, "s2", "Two", playCount = 2),
-                    song(sourceId, "s3", "Three", genre = "Rock", playCount = 4),
+                    song(sourceId, "s3", "Three", playCount = 4),
-                    song(sourceId, "s4", "Four", genre = "Classical", playCount = 0),
+                    song(sourceId, "s4", "Four", playCount = 0),
                 ),
             )
+            insertGenre(sourceId, "s1", 0, "Rock")
+            insertGenre(sourceId, "s3", 0, "Rock")
+            insertGenre(sourceId, "s2", 0, "Jazz")
+            insertGenre(sourceId, "s4", 0, "Classical")
 
             assertEquals(
                 listOf("Rock", "Jazz", "Classical"),
@@ -146,16 +150,17 @@ class LibraryHomeDaoTest {
         }
 
     @Test
-    fun genresComeFromTheGenreRelationsAndFallBackPerSong() =
+    fun genresComeFromTheStoredRelations() =
         runTest {
             val sourceId = source()
             val dao = db.libraryDao()
             dao.upsertSongs(
                 listOf(
-                    song(sourceId, "s1", "One", genre = "Legacy", playCount = 1),
+                    song(sourceId, "s1", "One", playCount = 1),
-                    song(sourceId, "s2", "Two", genre = "Legacy", playCount = 3),
+                    song(sourceId, "s2", "Two", playCount = 3),
                 ),
             )
+            insertGenre(sourceId, "s1", 0, "Legacy")
             insertGenre(sourceId, "s2", 0, "Rock")
             insertGenre(sourceId, "s2", 1, "Electronic")
 
@@ -190,18 +195,19 @@ class LibraryHomeDaoTest {
         }
 
     @Test
-    fun songsByGenreMatchesTheGenreRelationsWithFallback() =
+    fun songsByGenreReturnsSongsWithTheGenreRelation() =
         runTest {
             val sourceId = source()
             val dao = db.libraryDao()
             dao.upsertAlbums(listOf(album(sourceId, "al1", "Album", coverArt = "cover-1")))
             dao.upsertSongs(
                 listOf(
-                    song(sourceId, "s1", "Fallback", genre = "Rock"),
+                    song(sourceId, "s1", "Fallback"),
-                    song(sourceId, "s2", "Relation", genre = "Jazz"),
+                    song(sourceId, "s2", "Relation"),
-                    song(sourceId, "s3", "NotRock", genre = "Rock"),
+                    song(sourceId, "s3", "NotRock"),
                 ),
             )
+            insertGenre(sourceId, "s1", 0, "Rock")
             insertGenre(sourceId, "s2", 0, "Rock")
             insertGenre(sourceId, "s3", 0, "Jazz")
 
@@ -370,11 +376,14 @@ class LibraryHomeDaoTest {
             dao.upsertAlbums(listOf(album(sourceId, "al1", "Album", coverArt = "cover-1")))
             dao.upsertSongs(
                 listOf(
-                    song(sourceId, "s1", "Rock One", genre = "Rock"),
+                    song(sourceId, "s1", "Rock One"),
-                    song(sourceId, "s2", "Jazz One", genre = "Jazz"),
+                    song(sourceId, "s2", "Jazz One"),
-                    song(sourceId, "s3", "Rock Two", genre = "Rock"),
+                    song(sourceId, "s3", "Rock Two"),
                 ),
             )
+            insertGenre(sourceId, "s1", 0, "Rock")
+            insertGenre(sourceId, "s2", 0, "Jazz")
+            insertGenre(sourceId, "s3", 0, "Rock")
 
             val page = dao.songsByGenre(sourceId, "Rock").page()
             assertEquals(listOf("s1", "s3"), page.map { it.song.id })