postgresql數據庫連接數查詢

使用psql無法連接數據庫，並報錯 FATAL:53300

1. psql: FATAL: 53300: remaining connection slots are reserved for non-replication superuser connections

2. 普通用戶的連接已滿，保留用於非復制的超級用戶連接。

由於連接已滿，可以關閉空閑的連接

1）查詢當前所有連接的狀態

select datname,pid,application_name,state from pg_stat_activity;

2）關閉當前state為 idle 空閑狀態的連接

查看數據庫剩余連接數：

select max_conn-now_conn as resi_conn from (select setting::int8 as max_conn,(select count(*) from pg_stat_activity) as now_conn from pg_settings where name = 'max_connections') t;
查看為超級用戶保留的連接數: 
show superuser_reserved_connections;
psql: FATAL:  53300: sorry, too many clients already
數據庫連接已滿，無法建立新的連接。
1、關閉空閑連接
select datname,pid,application_name,state from pg_stat_activity; 
--查看目前所有的連接的進程id、應用名稱、狀態。
select pg_terminate_backend(pid) from pg_stat_activity; 
--通過pid終止空閑連接

當前總共正在使用的連接數：

select count(1) from pg_stat_activity;

顯示系統允許的最大連接數

show max_connections;

顯示系統保留的用戶數

show superuser_reserved_connections ;

 

–按照用戶分組查看

select usename, count(*) from pg_stat_activity group by usename order by count(*) desc;