merging releases

model.py

def merge_into_release(self, dest_release, src_release):
        """Transfers all data from a release to another and removes the source.
           Overwrites the destination where the release info differs.
           There is never loss of user information."""
        
        #merge = replace in dest + remove in src
        #move = insert in dest + remove in src
        
        def move_actions(model, dest_id, src_id):
            model.execute("update actions set object_id=? where object_id=?", src_id, dest_id)
            
        def replace_attachments(model, dest_id, src_id):
            model.execute("insert or replace into palettes (?, color1, color2, color3)"
                          " select color1, color2, color3 from palettes where id=?", dest_id, src_id)
                          
            model.execute("insert or replace into descriptions (?, description)"
                          " select description from descriptions where id=?", dest_id, src_id)
                          
            model.execute("insert or replace into links (?, type_id, target)"
                          " select type_id, target from links where id=?", dest_id, src_id)
            
        def replace_tracks(model, dest_id, src_id):
            (src_sides, dest_sides), _, _ = \
                zip(model.get_release_tracks(src_id)
                    model.get_release_tracks(dest_id))
            
            flatten = lambda lists: [item for list in lists for item in list]
            track_pairs = zip(*map(flatten, [src_sides, dest_sides]))
            
            if not all(src.runtime == dest.runtime for src, dest in track_pairs):
                raise ValueError("Track list runtimes didn't match")
                
            for track in dest_sides
        
        with self.transaction() as model:
            merge_tracks(self, dest_id, src_id)
            move_actions(self, dest_id, src_id)