playback: preserve null keys and ranged duplicate ranks

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

@@ -214,14 +214,34 @@ interface QueueDao {
     ): List<String>
 
     @Query(
-        "SELECT songs.*, albums.coverArt AS coverArt FROM songs " +
-            "LEFT JOIN albums ON albums.sourceId = songs.sourceId AND albums.id = songs.albumId " +
-            "WHERE songs.sourceId = :sourceId AND songs.id IN (:ids)",
+        "SELECT CASE WHEN EXISTS (SELECT 1 FROM songs WHERE sourceId = :sourceId AND albumId = :albumId AND id = :songId) " +
+            "THEN (SELECT COUNT(*) FROM songs ranked CROSS JOIN songs target " +
+            "WHERE ranked.sourceId = :sourceId AND ranked.albumId = :albumId " +
+            "AND target.sourceId = :sourceId AND target.albumId = :albumId AND target.id = :songId " +
+            "AND ((ranked.disc IS NULL AND target.disc IS NOT NULL) OR ranked.disc < target.disc OR " +
+            "(ranked.disc IS target.disc AND ((ranked.track IS NULL AND target.track IS NOT NULL) OR ranked.track < target.track OR " +
+            "(ranked.track IS target.track AND ranked.id < target.id))))) END",
     )
-    suspend fun songsByIds(
+    suspend fun albumRank(
         sourceId: Long,
-        ids: List<String>,
-    ): List<AlbumSongItem>
+        albumId: String,
+        songId: String,
+    ): Long?
+
+    @Query(
+        "SELECT CASE WHEN firstPosition IS NULL THEN NULL ELSE " +
+            "(SELECT COUNT(*) - 1 FROM playlist_songs " +
+            "JOIN songs ON songs.sourceId = playlist_songs.sourceId AND songs.id = playlist_songs.songId " +
+            "WHERE playlist_songs.sourceId = :sourceId AND playlist_songs.playlistId = :playlistId AND position <= firstPosition) END " +
+            "FROM (SELECT MIN(position) AS firstPosition FROM playlist_songs " +
+            "JOIN songs ON songs.sourceId = playlist_songs.sourceId AND songs.id = playlist_songs.songId " +
+            "WHERE playlist_songs.sourceId = :sourceId AND playlist_songs.playlistId = :playlistId AND songId = :songId)",
+    )
+    suspend fun playlistRank(
+        sourceId: Long,
+        playlistId: String,
+        songId: String,
+    ): Long?
 
     @Query("SELECT COUNT(*) FROM song_genres WHERE sourceId = :sourceId AND genre = :genre")
     suspend fun genreLength(
@@ -243,17 +263,6 @@ interface QueueDao {
         limit: Int,
     ): List<AlbumSongItem>
 
-    @Query(
-        "SELECT songs.id FROM song_genres " +
-            "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
-            "WHERE song_genres.sourceId = :sourceId AND song_genres.genre = :genre " +
-            "ORDER BY songs.sortName COLLATE NOCASE, songs.id",
-    )
-    suspend fun genreSongIds(
-        sourceId: Long,
-        genre: String,
-    ): List<String>
-
     @Query("SELECT COUNT(*) FROM song_downloads WHERE sourceId = :sourceId AND status = 'Completed'")
     suspend fun downloadedLength(sourceId: Long): Long
 
@@ -272,12 +281,6 @@ interface QueueDao {
         limit: Int,
     ): List<AlbumSongItem>
 
-    @Query(
-        "SELECT songs.id FROM songs WHERE sourceId = :sourceId AND starred IS NOT NULL " +
-            "ORDER BY starred DESC, sortName COLLATE NOCASE, id",
-    )
-    suspend fun starredSongIds(sourceId: Long): List<String>
-
     @Query(
         "SELECT songs.*, albums.coverArt AS coverArt FROM song_downloads d " +
             "JOIN songs ON songs.sourceId = d.sourceId AND songs.id = d.songId " +
@@ -290,12 +293,4 @@ interface QueueDao {
         offset: Long,
         limit: Int,
     ): List<AlbumSongItem>
-
-    @Query(
-        "SELECT songs.id FROM song_downloads d " +
-            "JOIN songs ON songs.sourceId = d.sourceId AND songs.id = d.songId " +
-            "WHERE d.sourceId = :sourceId AND d.status = 'Completed' " +
-            "ORDER BY d.downloadedAt DESC, songs.sortName COLLATE NOCASE, songs.id",
-    )
-    suspend fun downloadedSongIds(sourceId: Long): List<String>
 }

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

@@ -360,10 +360,7 @@ class LibraryRepository(
         sourceId: Long,
         albumId: String,
         songId: String,
-    ): Long {
-        val index = db.queueDao().albumSongIds(sourceId, albumId).indexOf(songId)
-        return if (index < 0) 0L else index.toLong()
-    }
+    ): Long = db.queueDao().albumRank(sourceId, albumId, songId) ?: 0L
 
     fun playlist(
         sourceId: Long,

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

@@ -209,6 +209,202 @@ data class Reanchored(
     val changed: Boolean,
 )
 
+private interface QueueKindResolver {
+    fun supportsKeyset(key: OrderKey): Boolean = false
+
+    suspend fun length(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+    ): Long
+
+    suspend fun rows(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        offset: Long,
+        limit: Int,
+    ): List<SongItem>
+
+    suspend fun rowsFrom(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        key: OrderKey,
+        skip: Long,
+        limit: Int,
+    ): List<SongItem>? = null
+
+    suspend fun rowsBefore(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        key: OrderKey,
+        skip: Long,
+        limit: Int,
+    ): List<SongItem>? = null
+
+    suspend fun rank(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        songId: String,
+    ): Long? = null
+}
+
+private val queueKindResolvers =
+    mapOf<QueueKind, QueueKindResolver>(
+        QueueKind.Song to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.songLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.song(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = if (entry.refId == songId && length(dao, entry) > 0) 0L else null
+            },
+        QueueKind.Playlist to
+            object : QueueKindResolver {
+                override fun supportsKeyset(key: OrderKey) = key.position != null
+
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.playlistLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.playlistSongs(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rowsFrom(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.playlistSongsFrom(entry.sourceId, entry.refId, key.position!!, skip, limit)
+
+                override suspend fun rowsBefore(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.playlistSongsBefore(entry.sourceId, entry.refId, key.position!!, skip, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = dao.playlistRank(entry.sourceId, entry.refId, songId)
+            },
+        QueueKind.Album to
+            object : QueueKindResolver {
+                override fun supportsKeyset(key: OrderKey) = key.disc != null && key.track != null
+
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.albumLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.albumSongs(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rowsFrom(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.albumSongsFrom(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
+
+                override suspend fun rowsBefore(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.albumSongsBefore(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = dao.albumRank(entry.sourceId, entry.refId, songId)
+            },
+        QueueKind.Artist to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.artistLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.artistSongs(entry.sourceId, entry.refId, offset, limit)
+            },
+        QueueKind.Genre to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.genreLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.genreSongs(entry.sourceId, entry.refId, offset, limit)
+            },
+        QueueKind.Downloaded to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.downloadedLength(entry.sourceId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.downloadedSongs(entry.sourceId, offset, limit)
+            },
+        QueueKind.Starred to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.starredLength(entry.sourceId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.starredSongs(entry.sourceId, offset, limit)
+            },
+    )
+
+private fun resolverFor(kind: QueueKind): QueueKindResolver = queueKindResolvers.getValue(kind)
+
 class QueueRepository(
     private val db: SubtracksDatabase,
 ) {
@@ -216,12 +412,6 @@ class QueueRepository(
 
     private val queueVersion = AtomicLong()
 
-    @Volatile
-    private var cachedFlatIds: List<String>? = null
-
-    @Volatile
-    private var cachedFlatVersion = -1L
-
     @Volatile
     private var shuffleRemoved: ShuffleState? = null
 
@@ -235,6 +425,9 @@ class QueueRepository(
     internal var offsetSeeks = 0L
         private set
 
+    internal var resolvedRowCount = 0L
+        private set
+
     private val cursorMutex = Mutex()
 
     fun playlistEntry(
@@ -388,7 +581,6 @@ class QueueRepository(
     }
 
     fun invalidateLibraryCache() {
-        cachedFlatIds = null
         lengthCache.clear()
         keyCache.clear()
         shuffleRemoved = null
@@ -409,8 +601,8 @@ class QueueRepository(
         snapshot: QueueSnapshot,
         songId: String,
     ): Long? {
-        val upIndex = idsFor(snapshot.upNext).indexOf(songId)
-        if (upIndex >= 0) return snapshot.anchorPlay + 1 + upIndex
+        val upIndex = flatIndexOf(snapshot.upNext, songId)
+        if (upIndex != null) return snapshot.anchorPlay + 1 + upIndex
         return combinedContextIndexOf(snapshot, songId)
     }
 
@@ -418,9 +610,8 @@ class QueueRepository(
         snapshot: QueueSnapshot,
         songId: String,
     ): Long? {
-        val flat = flatIds(snapshot).indexOf(songId)
-        if (flat < 0) return null
-        return snapshot.playContext(flat.toLong())?.let { snapshot.combined(it) }
+        val flat = flatIndexOf(snapshot.entries, songId) ?: return null
+        return snapshot.playContext(flat)?.let { snapshot.combined(it) }
     }
 
     suspend fun range(
@@ -633,7 +824,6 @@ class QueueRepository(
             }
         }
         queueVersion.incrementAndGet()
-        cachedFlatIds = null
     }
 
     private suspend fun writeUpNext(entries: List<QueueEntry>) {
@@ -650,34 +840,40 @@ class QueueRepository(
         queueVersion.incrementAndGet()
     }
 
-    private suspend fun flatIds(snapshot: QueueSnapshot): List<String> {
-        val cached = cachedFlatIds
-        if (cached != null && cachedFlatVersion == snapshot.version && cached.size.toLong() == snapshot.contextSize) return cached
-        val ids = idsFor(snapshot.entries)
-        cachedFlatIds = ids
-        cachedFlatVersion = snapshot.version
-        return ids
+    private suspend fun flatIndexOf(
+        entries: List<ResolvedQueueEntry>,
+        songId: String,
+    ): Long? {
+        var start = 0L
+        for (resolved in entries) {
+            val entry = resolved.entry
+            val rank = resolverFor(entry.kind).rank(dao, entry, songId)
+            if (rank != null && rank >= entry.offset && rank < entry.offset + resolved.length) {
+                return start + rank - entry.offset
+            }
+            val fallback = fallbackRank(entry, resolved.length, songId)
+            if (fallback != null) return start + fallback - entry.offset
+            start += resolved.length
+        }
+        return null
     }
 
-    private suspend fun idsFor(resolved: List<ResolvedQueueEntry>): List<String> {
-        val ids = ArrayList<String>()
-        for (entry in resolved) {
-            val ref = entry.entry
-            val entryIds =
-                when (ref.kind) {
-                    QueueKind.Song -> listOf(ref.refId)
-                    QueueKind.Album -> dao.albumSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Playlist -> dao.playlistSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Artist -> dao.artistSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Genre -> dao.genreSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Downloaded -> dao.downloadedSongIds(ref.sourceId)
-                    QueueKind.Starred -> dao.starredSongIds(ref.sourceId)
-                }
-            val from = ref.offset.toInt().coerceIn(0, entryIds.size)
-            val to = (ref.offset + entry.length).toInt().coerceIn(from, entryIds.size)
-            ids.addAll(entryIds.subList(from, to))
+    private suspend fun fallbackRank(
+        entry: QueueEntry,
+        length: Long,
+        songId: String,
+    ): Long? {
+        var offset = entry.offset
+        val end = entry.offset + length
+        while (offset < end) {
+            val limit = minOf(QUEUE_CHUNK.toLong(), end - offset).toInt()
+            val batch = rows(entry, offset, limit)
+            val index = batch.indexOfFirst { it.song.id == songId }
+            if (index >= 0) return offset + index
+            if (batch.size < limit) return null
+            offset += batch.size
         }
-        return ids
+        return null
     }
 
     private suspend fun contextPlayRange(
@@ -688,21 +884,11 @@ class QueueRepository(
         if (first > last) return emptyList()
         val items = mutableListOf<QueueWindowItem>()
         if (snapshot.shuffled) {
-            val sourceId =
-                snapshot.entries
-                    .firstOrNull()
-                    ?.entry
-                    ?.sourceId ?: return emptyList()
-            val ids = flatIds(snapshot)
-            val requested = mutableListOf<Pair<Long, String>>()
             for (play in first..last) {
-                val flat = snapshot.flatContext(play) ?: continue
-                val id = ids.getOrNull(flat.toInt()) ?: continue
-                requested += play to id
+                val located = snapshot.locateContext(play) ?: continue
+                val item = rows(located.first, located.first.offset + located.second, 1).firstOrNull() ?: continue
+                items += QueueWindowItem(snapshot.combined(play), item, playlistPosition = item.playlistPosition)
             }
-            if (requested.isEmpty()) return emptyList()
-            val byId = dao.songsByIds(sourceId, requested.map { it.second }.distinct()).associateBy { it.song.id }
-            requested.forEach { (play, id) -> byId[id]?.let { items += QueueWindowItem(snapshot.combined(play), it) } }
             return items
         }
         var start = 0L
@@ -757,27 +943,20 @@ class QueueRepository(
     ): List<SongItem> {
         if (entry.kind == QueueKind.Song) {
             offsetSeeks++
-            return dao.song(entry.sourceId, entry.refId, offset, limit)
+            return resolverFor(entry.kind).rows(dao, entry, offset, limit).also { resolvedRowCount += it.size }
         }
         val ref = QueueRef(entry.kind, entry.sourceId, entry.refId)
         val anchored = keyCache[ref]?.let { keyedRows(entry, offset, limit, it) }
         if (anchored != null) {
             keysetSeeks++
             if (anchored.isNotEmpty()) remember(ref, offset, anchored)
+            resolvedRowCount += anchored.size
             return anchored
         }
         offsetSeeks++
-        val fresh =
-            when (entry.kind) {
-                QueueKind.Playlist -> dao.playlistSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Album -> dao.albumSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Artist -> dao.artistSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Genre -> dao.genreSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Downloaded -> dao.downloadedSongs(entry.sourceId, offset, limit)
-                QueueKind.Starred -> dao.starredSongs(entry.sourceId, offset, limit)
-                QueueKind.Song -> emptyList()
-            }
+        val fresh = resolverFor(entry.kind).rows(dao, entry, offset, limit)
         if (fresh.isNotEmpty()) remember(ref, offset, fresh)
+        resolvedRowCount += fresh.size
         return fresh
     }
 
@@ -810,7 +989,7 @@ class QueueRepository(
         limit: Int,
         cursor: KeyCursor,
     ): List<SongItem>? {
-        if (!cursor.key.seekable(entry.kind)) return null
+        if (!resolverFor(entry.kind).supportsKeyset(cursor.key)) return null
         val from = cursor.ordinal
         // A backward seek from a far cursor is not cheaper than the offset query: the album
         // predicate is not sargable (it has to include NULL disc/track), so it scans the partition
@@ -836,43 +1015,14 @@ class QueueRepository(
         key: OrderKey,
         skip: Long,
         limit: Int,
-    ): List<SongItem> =
-        when (entry.kind) {
-            QueueKind.Playlist -> dao.playlistSongsFrom(entry.sourceId, entry.refId, key.position!!, skip, limit)
-            QueueKind.Album -> dao.albumSongsFrom(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
-            QueueKind.Artist -> emptyList()
-            QueueKind.Genre -> emptyList()
-            QueueKind.Downloaded -> emptyList()
-            QueueKind.Starred -> emptyList()
-            QueueKind.Song -> emptyList()
-        }
+    ): List<SongItem> = resolverFor(entry.kind).rowsFrom(dao, entry, key, skip, limit) ?: emptyList()
 
     private suspend fun rowsBefore(
         entry: QueueEntry,
         key: OrderKey,
         skip: Long,
         limit: Int,
-    ): List<SongItem> =
-        when (entry.kind) {
-            QueueKind.Playlist -> dao.playlistSongsBefore(entry.sourceId, entry.refId, key.position!!, skip, limit)
-            QueueKind.Album -> dao.albumSongsBefore(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
-            QueueKind.Artist -> emptyList()
-            QueueKind.Genre -> emptyList()
-            QueueKind.Downloaded -> emptyList()
-            QueueKind.Starred -> emptyList()
-            QueueKind.Song -> emptyList()
-        }
-
-    private fun OrderKey.seekable(kind: QueueKind): Boolean =
-        when (kind) {
-            QueueKind.Playlist -> position != null
-            QueueKind.Album -> disc != null && track != null
-            QueueKind.Artist -> false
-            QueueKind.Genre -> false
-            QueueKind.Downloaded -> false
-            QueueKind.Starred -> false
-            QueueKind.Song -> false
-        }
+    ): List<SongItem> = resolverFor(entry.kind).rowsBefore(dao, entry, key, skip, limit) ?: emptyList()
 
     private suspend fun lengthOf(
         entry: QueueEntry,
@@ -897,36 +1047,7 @@ class QueueRepository(
         )
 
     private suspend fun QueueEntry.resolvedLength(): Long {
-        val total =
-            when (kind) {
-                QueueKind.Song -> {
-                    dao.songLength(sourceId, refId)
-                }
-
-                QueueKind.Playlist -> {
-                    dao.playlistLength(sourceId, refId)
-                }
-
-                QueueKind.Album -> {
-                    dao.albumLength(sourceId, refId)
-                }
-
-                QueueKind.Artist -> {
-                    dao.artistLength(sourceId, refId)
-                }
-
-                QueueKind.Genre -> {
-                    dao.genreLength(sourceId, refId)
-                }
-
-                QueueKind.Downloaded -> {
-                    dao.downloadedLength(sourceId)
-                }
-
-                QueueKind.Starred -> {
-                    dao.starredLength(sourceId)
-                }
-            }
+        val total = resolverFor(kind).length(dao, this)
         val available = (total - offset).coerceAtLeast(0)
         return count?.coerceAtMost(available) ?: available
     }

app/src/test/kotlin/com/subtracks/data/repo/QueueKeysetTest.kt

@@ -150,6 +150,18 @@ class QueueKeysetTest {
             assertTrue("backward keyset seeks", repository.keysetSeeks > beforeBackward)
         }
 
+    @Test
+    fun scanningAnAlbumWithNullDiscAndTrackForwardFallsBackToOffsetRows() =
+        runTest {
+            seedLibrary()
+            repository.replace(listOf(repository.albumEntry(1, "mixed")))
+            val snapshot = repository.snapshot()
+
+            val resolved = (0 until snapshot.size).map { repository.itemAt(snapshot, it)?.song?.id }
+
+            assertEquals(listOf("n1", "n2", "s1", "s2"), resolved)
+        }
+
     @Test
     fun scanningAnAlbumWithNullDiscAndTrackBackwardsResolvesEveryRow() =
         runTest {
@@ -260,6 +272,22 @@ class QueueKeysetTest {
             assertTrue(ids.all { it in expected })
         }
 
+    @Test
+    fun thePlaylistWindowQuerySeeksThePositionIndex() =
+        runTest {
+            seedLibrary()
+            val plan =
+                queryPlan(
+                    "SELECT songs.*, playlist_songs.position AS playlistPosition, albums.coverArt AS coverArt " +
+                        "FROM playlist_songs JOIN songs ON songs.sourceId = playlist_songs.sourceId " +
+                        "AND songs.id = playlist_songs.songId LEFT JOIN albums ON albums.sourceId = songs.sourceId " +
+                        "AND albums.id = songs.albumId WHERE playlist_songs.sourceId = 1 " +
+                        "AND playlist_songs.playlistId = 'pl1' ORDER BY playlist_songs.position LIMIT 51 OFFSET 100000",
+                )
+
+            assertTrue(plan.joinToString("\n"), plan.any { it.contains("sqlite_autoindex_playlist_songs_1") })
+        }
+
     @Test
     fun theAlbumKeysetQuerySeeksTheOrderIndex() =
         runTest {

app/src/test/kotlin/com/subtracks/data/repo/QueueRepositoryTest.kt

@@ -727,6 +727,32 @@ class QueueRepositoryTest {
             assertEquals(listOf("s1", "s2", "s3"), resolveAll(restored))
         }
 
+    @Test
+    fun shuffledLargeContextWindowOnlyResolvesRequestedRows() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("huge", "Huge")))
+            db.useWriterConnection { transactor ->
+                transactor.usePrepared(
+                    "WITH RECURSIVE n(x) AS (VALUES(0) UNION ALL SELECT x + 1 FROM n WHERE x < 199999) " +
+                        "INSERT INTO playlist_songs SELECT 1, 'huge', 's1', x FROM n",
+                ) { statement ->
+                    statement.step()
+                }
+            }
+            repository.snapshotAfter(listOf(repository.playlistEntry(1, "huge")))
+            repository.setShuffle(42L)
+            val snapshot = repository.snapshot()
+
+            val window = repository.window(snapshot, center = 100_000, radius = 25)
+
+            assertEquals(200_000L, snapshot.contextSize)
+            assertEquals(51, window.size)
+            assertEquals(51L, repository.resolvedRowCount)
+            assertEquals((99_975L..100_025L).toList(), window.map { it.position })
+            assertTrue(window.all { it.item.song.id == "s1" })
+        }
+
     @Test
     fun shuffledRangeResolvesEntriesInPositionOrder() =
         runTest {
@@ -851,6 +877,55 @@ class QueueRepositoryTest {
             }
         }
 
+    @Test
+    fun contextIndexUsesTheFirstDuplicateOrdinalAcrossSparsePositions() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("duplicates", "Duplicates")))
+            db.libraryDao().upsertPlaylistSongs(
+                listOf(
+                    PlaylistSong(1, "duplicates", "s2", 10),
+                    PlaylistSong(1, "duplicates", "s1", 20),
+                    PlaylistSong(1, "duplicates", "s2", 30),
+                ),
+            )
+            val snapshot = repository.snapshotAfter(listOf(repository.playlistEntry(1, "duplicates")))
+
+            assertEquals(0L, repository.combinedContextIndexOf(snapshot, "s2"))
+            assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s1"))
+        }
+
+    @Test
+    fun contextIndexFindsADuplicateInsideTheEntryRange() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("duplicates", "Duplicates")))
+            db.libraryDao().upsertPlaylistSongs(
+                listOf(
+                    PlaylistSong(1, "duplicates", "s2", 10),
+                    PlaylistSong(1, "duplicates", "s1", 20),
+                    PlaylistSong(1, "duplicates", "s2", 30),
+                ),
+            )
+            val entry = repository.playlistEntry(1, "duplicates").copy(rangeStart = 1, rangeEnd = 2)
+            val snapshot = repository.snapshotAfter(listOf(entry))
+
+            assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s2"))
+        }
+
+    @Test
+    fun contextIndexFallsBackToBoundedRowsForGenre() =
+        runTest {
+            seedLibrary()
+            insertGenre("s1", "Rock")
+            insertGenre("s3", "Rock")
+            insertGenre("s4", "Rock")
+            val snapshot = repository.snapshotAfter(listOf(repository.genreEntry(1, "Rock")))
+
+            assertEquals(2L, repository.combinedContextIndexOf(snapshot, "s4"))
+            assertTrue(repository.resolvedRowCount <= QUEUE_CHUNK)
+        }
+
     @Test
     fun upNextCombinedIndexOfCountsFromTheAnchorIntoTheBlock() =
         runTest {