更新计数器触发的PostgreSQL

Question

我有一个表像发送此

----------------------------------------------------------------------------------- 
id         | notification_sent | times_notification_sent 
----------------------------------------------------------------------------------- 
4a1717a2-6e1e-4af6-aa34-8262899aa060 | t     | 0 

这里通知是布尔字段和times_notification_sent为int。我正在尝试创建触发器，当notification_sent从true更改为false时，会将times_notification_sent递增1。

我正在使用下面的函数和触发器，但它不工作。

CREATE OR REPLACE FUNCTION update_sent_counter_for_watch() RETURNS TRIGGER 
LANGUAGE plpgsql 
AS $$ BEGIN 
IF OLD.notification_sent IS TRUE AND NEW.notification_sent IS FALSE THEN 
    UPDATE "watch" SET "times_notification_sent" = "times_notification_sent" + 1 WHERE "id" = OLD."id"; 
END IF; 
END; 
$$; 

CREATE TRIGGER "update_times_sent_counter" AFTER UPDATE OF "times_notification_sent" ON "public"."watch" 
FOR EACH ROW 
WHEN (OLD.notification_sent IS DISTINCT FROM NEW.notification_sent) 
EXECUTE PROCEDURE "public"."update_sent_counter_for_watch"(); 

Answer 1

你有两个错误：

你并不需要一个update，只是分配新值：

CREATE OR REPLACE FUNCTION update_sent_counter_for_watch() 
    RETURNS TRIGGER 
    LANGUAGE plpgsql 
AS 
$$ 
BEGIN 
    IF OLD.notification_sent IS TRUE AND NEW.notification_sent IS FALSE THEN 
    new.times_notification_sent := old.times_notification_sent + 1; 
    END IF; 
    RETURN new; 
END; 
$$; 

而且你不能在after update TRIGER更改值，您需要将其更改为before触发器：

CREATE TRIGGER "update_times_sent_counter" BEFORE UPDATE OF "times_notification_sent" 
    ON "public"."watch" 
    FOR EACH ROW 
WHEN (OLD.notification_sent IS DISTINCT FROM NEW.notification_sent) 
EXECUTE PROCEDURE "public"."update_sent_counter_for_watch"();