Implemented the "remove duplicates" feature.

app/src/main/java/org/schabi/newpipe/database/playlist/dao/PlaylistStreamDAO.java

@@ -84,14 +84,22 @@ public interface PlaylistStreamDAO extends BasicDAO<PlaylistStreamEntity> {
             + " ORDER BY " + PLAYLIST_NAME + " COLLATE NOCASE ASC")
     Flowable<List<PlaylistMetadataEntry>> getPlaylistMetadata();
 
+    @RewriteQueriesToDropUnusedColumns
     @Transaction
-    @Query("DELETE FROM " + PLAYLIST_STREAM_JOIN_TABLE
-            + " WHERE " + JOIN_PLAYLIST_ID + "=:playlistId"
-            + " AND " + JOIN_STREAM_ID + " IN ("
-            + " SELECT " + JOIN_STREAM_ID
+    @Query("SELECT *, MIN(" + JOIN_INDEX + ") FROM " + STREAM_TABLE + " INNER JOIN "
+            + "(SELECT " + JOIN_STREAM_ID + "," + JOIN_INDEX
             + " FROM " + PLAYLIST_STREAM_JOIN_TABLE
-            + " WHERE " + JOIN_PLAYLIST_ID + "=:playlistId"
-            + " GROUP BY " + JOIN_STREAM_ID
-            + " HAVING COUNT(*) > 1 )" )
-    Flowable<List<PlaylistMetadataEntry>> removeDuplicates(long playlistId);
+            + " WHERE " + JOIN_PLAYLIST_ID + " = :playlistId)"
+            + " ON " + STREAM_ID + " = " + JOIN_STREAM_ID
+            + " LEFT JOIN "
+            + "(SELECT " + JOIN_STREAM_ID + " AS " + JOIN_STREAM_ID_ALIAS + ", "
+            + STREAM_PROGRESS_MILLIS
+            + " FROM " + STREAM_STATE_TABLE + " )"
+            + " ON " + STREAM_ID + " = " + JOIN_STREAM_ID_ALIAS
+            + " GROUP BY " + STREAM_ID
+            + " ORDER BY " + JOIN_INDEX + " ASC")
+    Flowable<List<PlaylistStreamEntry>> getStreamsWithoutDuplicates(long playlistId);
+
+
+
 }