PostgreSQL 查询最近运行的的SQL 语句：
SELECT procpid,start,now() - start AS lap,current_query FROM (SELECT
backendid, pg_stat_get_backend_pid(S.backendid) AS procpid, pg_stat_get_backend_activity_start(S.backendid) AS start,pg_stat_get_backend_activity(S.backendid) AS current_query FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS S
) AS S
WHERE
current_query <> '<IDLE>'
ORDER BY
lap DESC;
