library: keep artist art maintenance self-healing and cheap

Move change detection into a desired CTE with UPDATE ... FROM so mass updates do not turn the trailing WHERE into a quadratic correlated scan, and so no-op passes write zero rows. Fold the trigger optimization into the 35->36 migration and re-check/rewrite it from onOpen, so a future migration cannot silently restore the full UPDATE triggers. Re-resolve artist detail art when the active source becomes ready, and cover artist search renames in a Room-level test.

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

@@ -118,6 +118,10 @@ internal object ArtistSearchTriggerOptimization : RoomDatabase.Callback() {
     override suspend fun onCreate(connection: SQLiteConnection) {
         optimizeArtistSearchTriggers(connection)
     }
+
+    override suspend fun onOpen(connection: SQLiteConnection) {
+        if (!artistSearchTriggersOptimized(connection)) optimizeArtistSearchTriggers(connection)
+    }
 }
 
 internal object SqliteLifecycleLogging : RoomDatabase.Callback() {

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

@@ -225,15 +225,15 @@ internal const val ARTIST_ART_UPDATE_SQL =
         "ROW_NUMBER() OVER (PARTITION BY artistId ORDER BY coverRank) AS coverRank FROM unique_downloaded), " +
         "downloaded_covers AS (SELECT artistId, group_concat(coverArt, char(31)) AS coverArts FROM (" +
         "SELECT artistId, coverArt, coverRank FROM downloaded_deduped WHERE coverRank <= 4 ORDER BY artistId, coverRank" +
-        ") GROUP BY artistId) " +
-        "UPDATE artists SET " +
-        "coverArts = COALESCE((SELECT coverArts FROM covers WHERE covers.artistId = artists.id), ''), " +
-        "downloadedCoverArts = COALESCE((SELECT coverArts FROM downloaded_covers " +
-        "WHERE downloaded_covers.artistId = artists.id), '') " +
-        "WHERE sourceId = :sourceId AND (" +
-        "coverArts != COALESCE((SELECT coverArts FROM covers WHERE covers.artistId = artists.id), '') " +
-        "OR downloadedCoverArts != COALESCE((SELECT coverArts FROM downloaded_covers " +
-        "WHERE downloaded_covers.artistId = artists.id), ''))"
+        ") GROUP BY artistId), " +
+        "desired AS (SELECT artists.rowid AS rowid, " +
+        "COALESCE((SELECT coverArts FROM covers WHERE covers.artistId = artists.id), '') AS coverArts, " +
+        "COALESCE((SELECT coverArts FROM downloaded_covers " +
+        "WHERE downloaded_covers.artistId = artists.id), '') AS downloadedCoverArts " +
+        "FROM artists WHERE artists.sourceId = :sourceId) " +
+        "UPDATE artists SET coverArts = desired.coverArts, downloadedCoverArts = desired.downloadedCoverArts " +
+        "FROM desired WHERE artists.rowid = desired.rowid AND " +
+        "(artists.coverArts != desired.coverArts OR artists.downloadedCoverArts != desired.downloadedCoverArts)"
 
 internal const val DOWNLOADED_ARTIST_ART_UPDATE_SQL =
     "WITH downloaded_albums AS (SELECT DISTINCT artistId, albumId FROM ($DOWNLOADED_COVER_ALBUM_ROWS) " +
@@ -248,12 +248,14 @@ internal const val DOWNLOADED_ARTIST_ART_UPDATE_SQL =
         "ROW_NUMBER() OVER (PARTITION BY artistId ORDER BY coverRank) AS coverRank FROM unique_downloaded), " +
         "downloaded_covers AS (SELECT artistId, group_concat(coverArt, char(31)) AS coverArts FROM (" +
         "SELECT artistId, coverArt, coverRank FROM downloaded_deduped WHERE coverRank <= 4 ORDER BY artistId, coverRank" +
-        ") GROUP BY artistId) " +
-        "UPDATE artists SET downloadedCoverArts = COALESCE((SELECT coverArts FROM downloaded_covers " +
-        "WHERE downloaded_covers.artistId = artists.id), '') " +
-        "WHERE sourceId = :sourceId AND id IN (:artistIds) AND " +
-        "downloadedCoverArts != COALESCE((SELECT coverArts FROM downloaded_covers " +
-        "WHERE downloaded_covers.artistId = artists.id), '')"
+        ") GROUP BY artistId), " +
+        "desired AS (SELECT artists.rowid AS rowid, " +
+        "COALESCE((SELECT coverArts FROM downloaded_covers " +
+        "WHERE downloaded_covers.artistId = artists.id), '') AS downloadedCoverArts " +
+        "FROM artists WHERE artists.sourceId = :sourceId AND artists.id IN (:artistIds)) " +
+        "UPDATE artists SET downloadedCoverArts = desired.downloadedCoverArts " +
+        "FROM desired WHERE artists.rowid = desired.rowid AND " +
+        "artists.downloadedCoverArts != desired.downloadedCoverArts"
 
 internal const val ARTISTS_FILTER =
     "FROM artists WHERE sourceId = :sourceId " +

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

@@ -701,16 +701,20 @@ val MIGRATION_35_36 =
             connection.execSQL("ALTER TABLE `artists` ADD COLUMN `artistImageUrl` TEXT")
             connection.execSQL("ALTER TABLE `artists` ADD COLUMN `coverArts` TEXT NOT NULL DEFAULT ''")
             connection.execSQL("ALTER TABLE `artists` ADD COLUMN `downloadedCoverArts` TEXT NOT NULL DEFAULT ''")
+            optimizeArtistSearchTriggers(connection)
             backfillArtistArt(connection)
         }
     }
 
-val MIGRATION_36_37 =
-    object : Migration(36, 37) {
-        override suspend fun migrate(connection: SQLiteConnection) {
-            optimizeArtistSearchTriggers(connection)
-        }
+internal fun artistSearchTriggersOptimized(connection: SQLiteConnection): Boolean {
+    val triggers = mutableListOf<String>()
+    connection.prepare("SELECT sql FROM sqlite_master WHERE type = 'trigger' AND name IN (?, ?)").use { statement ->
+        statement.bindText(1, "room_fts_content_sync_artist_search_BEFORE_UPDATE")
+        statement.bindText(2, "room_fts_content_sync_artist_search_AFTER_UPDATE")
+        while (statement.step()) triggers += statement.getText(0)
     }
+    return triggers.size == 2 && triggers.all { it.contains("UPDATE OF `name`, `sortName`") }
+}
 
 internal fun optimizeArtistSearchTriggers(connection: SQLiteConnection) {
     connection.execSQL("DROP TRIGGER IF EXISTS room_fts_content_sync_artist_search_BEFORE_UPDATE")
@@ -778,5 +782,4 @@ val MIGRATIONS: Array<Migration> =
         MIGRATION_33_34,
         MIGRATION_34_35,
         MIGRATION_35_36,
-        MIGRATION_36_37,
     )

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

@@ -57,7 +57,7 @@ import com.subtracks.data.model.UpNextEntry
         SongDownload::class,
         PendingAction::class,
     ],
-    version = 37,
+    version = 36,
     exportSchema = true,
 )
 @ColumnTypeConverters(

app/src/main/kotlin/com/subtracks/data/repo/SourceRepository.kt

@@ -70,6 +70,9 @@ class SourceRepository(
     private val _offline = MutableStateFlow(false)
     val offline: StateFlow<Boolean> = _offline
 
+    private val _activeSource = MutableStateFlow<Long?>(null)
+    val activeSource: StateFlow<Long?> = _activeSource
+
     fun downloadsAllowedOverMetered(): Boolean = allowMeteredDownloads
 
     fun setOfflineMode(enabled: Boolean) {
@@ -110,6 +113,7 @@ class SourceRepository(
                     Log.i("net", "active source -> ${config?.name ?: "none"}")
                 }
                 active = config?.let { ActiveSource(it.id, it.toMusicSource(quality, concurrency)) }
+                _activeSource.value = config?.id
                 _quality.value = quality
                 if (sourceChanged && config != null && config.useTokenAuth && !_offline.value) {
                     scope.launch {

app/src/main/kotlin/com/subtracks/ui/library/ArtistDetailViewModel.kt

@@ -17,7 +17,6 @@ import com.subtracks.ui.components.ArtistArt
 import com.subtracks.ui.components.artistArt
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -143,8 +142,13 @@ class ArtistDetailViewModel(
 
     init {
         viewModelScope.launch {
-            combine(artist.filterNotNull(), sourceRepository.offline) { loaded, _ -> loaded }
-                .collectLatest { loaded ->
+            combine(
+                artist.filterNotNull(),
+                sourceRepository.offline,
+                sourceRepository.activeSource,
+            ) { loaded, _, activeSource -> loaded to activeSource }
+                .collectLatest { (loaded, activeSource) ->
+                    if (activeSource == null) return@collectLatest
                     val hero = sourceRepository.artistArt(loaded, forIcon = false)
                     val icon = sourceRepository.artistArt(loaded, forIcon = true)
                     _art.value = hero.image ?: hero.covers.firstOrNull()