函数可以检测触发事件类型吗? [英] Can a function detect the trigger event type?

问题描述

我正在使用函数

CREATE FUNCTION myfunc() RETURNS trigger AS $$ ... $$ LANGUAGE plpgsql;

带有触发器，

    CREATE TRIGGER mycheck BEFORE INSERT OR UPDATE ON t
       FOR EACH ROW EXECUTE PROCEDURE myfunc();

我现在的问题是在myfunc()主体中表达有关事件的条件，例如plpgsql

My problem now is to express in the body of myfunc() a condition about events, a plpgsql like

    IF TRIGGER_EVENT_WAS_INSERT THEN ...doThis... END IF;

如何表达这种情况?(请参阅我是否具有"INSERT OR UPDATE"触发事件)

How to express this condition? (see that I have "INSERT OR UPDATE" trigger event)

我正在使用PostgreSQL v9.1.

I am using PostgreSQL v9.1.

推荐答案

是， TG_OP . 每个文档:

TG_OP
数据类型文本； INSERT，UPDATE，DELETE或TRUNCATE的字符串，说明触发了哪个操作.

TG_OP
Data type text; a string of INSERT, UPDATE, DELETE, or TRUNCATE telling for which operation the trigger was fired.

注意每种情况下的返回.有时您想要RETURN NEW，如果DELETE则未定义，反之亦然.如果它变得太复杂，则将其分为多个触发器，分别在单独的事件上调用.

Careful what you return in each case. Sometimes you want to RETURN NEW, which is not defined in case of a DELETE or vice versa. If it gets too complex, rather split into multiple triggers, called on separate events.

示例:

IF TG_OP = 'DELETE' THEN
   -- do something
   RETURN OLD;  -- depends!
ELSIF TG_OP = 'UPDATE' THEN  
   -- do something
   RETURN NEW;  -- depends!
END IF;

相关答案中的更多代码示例.

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