db.py 文件源码

def _cull(self, db, cursor, now):
        if self._cull_frequency == 0:
            self.clear()
        else:
            connection = connections[db]
            table = connection.ops.quote_name(self._table)
            cursor.execute("DELETE FROM %s WHERE expires < %%s" % table,
                           [connection.ops.adapt_datetimefield_value(now)])
            cursor.execute("SELECT COUNT(*) FROM %s" % table)
            num = cursor.fetchone()[0]
            if num > self._max_entries:
                cull_num = num // self._cull_frequency
                cursor.execute(
                    connection.ops.cache_key_culling_sql() % table,
                    [cull_num])
                cursor.execute("DELETE FROM %s "
                               "WHERE cache_key < %%s" % table,
                               [cursor.fetchone()[0]])