```postgresql
SELECT locker.pid,
       pc.relname,
       locker.mode,
       locker_act.application_name,
       least(query_start,xact_start) start_time,
       locker_act.state,
       CASE
           WHEN granted='f' THEN
               'wait_lock'
           WHEN granted='t' THEN
               'get_lock'
           END lock_satus,current_timestamp - least(query_start,xact_start) AS runtime,
       locker_act.query
FROM pg_locks locker,pg_stat_activity locker_act, pg_class pc
WHERE locker.pid=locker_act.pid
  AND NOT locker.pid=pg_backend_pid()
  AND application_name<>'pg_statsinfod'
  AND locker.relation = pc.oid
  AND pc.reltype<>0 --and pc.relname='t'
ORDER BY  runtime desc;


SELECT pg_terminate_backend(14448)

```



```postgresql
-- 查看表的总大小，包括索引大小  
select pg_size_pretty(pg_total_relation_size('test')); 

-- 以KB，MB，GB的方式来查看表大小
select pg_size_pretty(pg_relation_size('test'));     

-- 查看最大连接数
show max_connections;

-- 查看当前连接数
SELECT COUNT(*) from pg_stat_activity;


```