如何查看当前数据库中正在执行的sql语句

--SELECT SQL process--
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