db.py 文件源码

def has_key(self, key, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        connection = connections[db]
        table = connection.ops.quote_name(self._table)

        if settings.USE_TZ:
            now = datetime.utcnow()
        else:
            now = datetime.now()
        now = now.replace(microsecond=0)

        with connection.cursor() as cursor:
            cursor.execute("SELECT cache_key FROM %s "
                           "WHERE cache_key = %%s and expires > %%s" % table,
                           [key, connection.ops.adapt_datetimefield_value(now)])
            return cursor.fetchone() is not None