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在postgresql中结束掉正在执行的SQL语句操作

2020-12-30 14:40:01 作者：hy.ding

这篇文章主要介绍了在postgresql中结束掉正在执行的SQL语句操作，具有很好的参考价值，希望对大家有所帮助。一起跟随小编过来看看吧

结束进程两种方式：

SELECT pg_cancel_backend(PID)

取消后台操作，回滚未提交事物 (select);

SELECT pg_terminate_backend(PID)

中断session，回滚未提交事物(select、update、delete、drop);

SELECT * FROM pg_stat_activity;

根据datid=10841

SELECT pg_terminate_backend (10841);

补充：PostgreSQL无法在PL / pgSQL中开始/结束事务

我正在寻求澄清如何确保plpgsql函数中的原子事务,以及为数据库进行此特定更改设置了隔离级别.

在下面显示的plpgsql函数中,我想确保BOTH的删除和插入成功.当我尝试将它们包装在一个事务中时,我收到一个错误：

错误：无法在PL / pgSQL中开始/结束事务.

如果另一个用户在此功能已删除自定义记录之后,但在此函数有机会插入自定义记录之前,为情况(RAIN,NIGHT,45MPH)添加了默认行为,下面的函数执行过程中会发生什么？是否有一个隐式事务包装插入和删除,以便如果另一个用户已经更改了此函数引用的任何一个行,两者都将回滚？我可以设置此功能的隔离级别吗？

create function foo(v_weather varchar(10), v_timeofday varchar(10), v_speed varchar(10),
 v_behavior varchar(10))
 returns setof CUSTOMBEHAVIOR
 as $body$
 begin
 -- run-time error if either of these lines is un-commented
 -- start transaction ISOLATION LEVEL READ COMMITTED;
 -- or, alternatively, set transaction ISOLATION LEVEL READ COMMITTED;
  delete from CUSTOMBEHAVIOR 
  where weather = 'RAIN' and timeofday = 'NIGHT' and speed= '45MPH' ;
 -- if there is no default behavior insert a custom behavior
 if not exists
  (select id from DEFAULTBEHAVIOR where a = 'RAIN' and b = 'NIGHT' and c= '45MPH') then 
  insert into CUSTOMBEHAVIOR
  (weather, timeofday, speed, behavior)
  values
  (v_weather, v_timeofday, v_speed, v_behavior);
 end if;
 return QUERY
 select * from CUSTOMBEHAVIOR where ... ;
 -- commit;
 end
 $body$
 LANGUAGE plpgsql

一个plpgsql函数在事务中自动运行.这一切都成功了,一切都失败了.

我引用the manual on plpgsql functions：

Functions and trigger procedures are always executed within a transaction established by an outer query — they cannot start or commit that transaction, since there would be no context for them to execute in. However, a block containing an EXCEPTION clause effectively forms a subtransaction that can be rolled back without affecting the outer transaction.

所以,如果你需要,你可以捕获理论上可能发生的异常(但是不大可能).

Details on trapping errors in the manual.

您的功能审查和简化：

CREATE FUNCTION foo(v_weather text
   , v_timeofday text
   , v_speed text
   , v_behavior text)
 RETURNS SETOF custombehavior AS
$body$
BEGIN
DELETE FROM custombehavior
WHERE weather = 'RAIN'
AND timeofday = 'NIGHT'
AND speed = '45MPH';
INSERT INTO custombehavior (weather, timeofday, speed, behavior)
SELECT v_weather, v_timeofday, v_speed, v_behavior
WHERE NOT EXISTS (
 SELECT 1 FROM defaultbehavior
 WHERE a = 'RAIN'
 AND b = 'NIGHT'
 AND c = '45MPH'
 );
RETURN QUERY
SELECT * FROM custombehavior WHERE ... ;
END
$body$LANGUAGE plpgsql

以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。如有错误或未考虑完全的地方，望不吝赐教。

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