Improve performance of save_playlist

app/models.py

@@ -593,6 +593,27 @@ class PlaylistRows(Base):
             .values(row_number=PlaylistRows.row_number + move_by)
         )
 
+    @staticmethod
+    def indexed_by_row(session: Session, playlist_id: int) -> dict:
+        """
+        Return a dictionary of playlist_rows indexed by row number for
+        the passed playlist_id.
+        """
+
+        plrs = session.execute(
+            select(PlaylistRows)
+            .where(
+                PlaylistRows.playlist_id == playlist_id,
+            )
+            .order_by(PlaylistRows.row_number)
+        ).scalars().all()
+
+        result = {}
+        for plr in plrs:
+            result[plr.row_number] = plr
+
+        return result
+
 
 class Settings(Base):
     """Manage settings"""

app/playlists.py

@@ -827,11 +827,11 @@ class PlaylistTab(QTableWidget):
         the row number is correct (in case tracks have been reordered).
         """
 
+        plr_dict = PlaylistRows.indexed_by_row(session, self.playlist_id)
         for row in range(self.rowCount()):
-            plr = session.get(PlaylistRows, self._get_playlistrow_id(row))
             # Set the row number and playlist id (even if correct)
-            plr.row_number = row
-            plr.playlist_id = self.playlist_id
+            plr_dict[row].row_number = row
+            plr_dict[row].playlist_id = self.playlist_id
 
         # Any rows in the database with a row_number higher that the
         # current value of 'row' should not be there. Commit session