分析作业是否被阻塞

数据库系统运行时，在某些业务场景下查询语句会被阻塞，导致语句运行时间过长，可以强制结束有问题的会话。

操作步骤

查看阻塞的查询语句及阻塞查询的表、模式信息。

SELECT w.query as waiting_query,
w.pid as w_pid,
w.usename as w_user,
l.query as locking_query,
l.pid as l_pid,
l.usename as l_user,
t.schemaname || '.' || t.relname as tablename
from pg_stat_activity w join pg_locks l1 on w.pid = l1.pid
and not l1.granted join pg_locks l2 on l1.relation = l2.relation
and l2.granted join pg_stat_activity l on l2.pid = l.pid join pg_stat_user_tables t on l1.relation = t.relid
where w.waiting;

该查询返回线程ID、用户信息、查询状态，以及导致阻塞的表、模式信息。

使用如下命令结束相应的会话。其中，139834762094352为线程ID。
1

SELECT PG_TERMINATE_BACKEND(139834762094352);
显示类似如下信息，表示结束会话成功。
```
 PG_TERMINATE_BACKEND
----------------------
 t
(1 row)
```
显示类似如下信息，表示用户正在尝试结束当前会话，此时仅会重连会话，而不是结束会话。
```
FATAL:  terminating connection due to administrator command
FATAL:  terminating connection due to administrator command
The connection to the server was lost. Attempting reset: Succeeded.
```
gsql客户端使用PG_TERMINATE_BACKEND函数终止本会话后台线程时，客户端不会退出而是自动重连。