db.py 文件源码

def num_connections(self):
        """Returns the number of existing connections to the database.  If
           there are >1 connections, a new Ravel base implementation cannot be
           loaded into the database.
           returns: the number of existing connections to the database"""
        try:
            self.cursor.execute("SELECT * FROM pg_stat_activity WHERE "
                                "datname='{0}'".format(self.name))

            # ignore cursor connection
            return len(self.cursor.fetchall()) - 1
        except psycopg2.DatabaseError, e:
            logger.warning("error loading schema: %s", self.fmt_errmsg(e))

        return 0