Mark this update as complete.

        IMPORTANT, If the marker table doesn't exist,
        the connection transaction will be aborted and the connection reset.
        Then the marker table will be created.

def touch(self, connection=None):
        """
        Mark this update as complete.

        IMPORTANT, If the marker table doesn't exist,
        the connection transaction will be aborted and the connection reset.
        Then the marker table will be created.
        """
        self.create_marker_table()

        if connection is None:
            connection = self.connect()
            connection.autocommit = True  # if connection created here, we commit it here

        connection.cursor().execute(
            """INSERT INTO {marker_table} (update_id, target_table)
               VALUES (%s, %s)
               ON DUPLICATE KEY UPDATE
               update_id = VALUES(update_id)
            """.format(marker_table=self.marker_table),
            (self.update_id, self.table)
        )
        # make sure update is properly marked
        assert self.exists(connection)