select count(1) from pg_stat_activity;

show max_connections;

max_connections = 500

//查看過期連接
select * from pg_stat_activity where state = 'idle'
 
//刪除連接，括號里傳pid
select pg_terminate_backend(25800);
 
//查看最大連接數(shù)
show max_connections;
 
//修改最大連接數(shù)，需要superuser權(quán)限
alter system set max_connections= 1000;