如何查詢postgresql 執行過的sql語句[未試驗]

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; 

procpid：進程id 
start：進程開始時間 
lap：通過時間 
current_query：執行中的sql 
怎樣中止正在執行的sql 
SELECT pg_cancel_backend(進程id); 
或者用系統函數 
kill -9 進程id;