def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def _loadapp(self, proxy_config_path):
        """
        Load a proxy from an app.conf to get the memcache_ring

        :returns: the memcache_ring of the memcache middleware filter
        """
        with mock.patch('swift.proxy.server.Ring'):
            app = loadapp(proxy_config_path)
        memcache_ring = None
        while True:
            memcache_ring = getattr(app, 'memcache', None)
            if memcache_ring:
                break
            app = app.app
        return memcache_ring