Re: trigger conversion advice needed
От | Clint Stotesbery |
---|---|
Тема | Re: trigger conversion advice needed |
Дата | |
Msg-id | BAY9-F41p68V8zDv60g0001fbb1@hotmail.com обсуждение исходный текст |
Ответ на | trigger conversion advice needed ("Clint Stotesbery" <cstotes@hotmail.com>) |
Список | pgsql-sql |
Thanks for the advice Tom. I figured out why my create trigger statement wouldn't compile. Postgres expects a FOR EACH ROW or FOR EACH STATEMENT clause before the EXECUTE portion. Oracle assumes a statement level trigger unless you specify it to be for each row. In addition Oracle allows for specific columns to be monitored for updates like I had in the Oracle trigger (AFTER UPDATE OR INSERT OF order_date ON orders). Well I ended up adding FOR EACH STATEMENT to the Postgres version after the first email. I got a message back that said statement triggers weren't implemented in Postgres yet even though according to the 7.3 docs it can be used. I looked at the changelog for 7.4 and it said: "Add statement-level triggers (Neil) While this allows a trigger to fire at the end of a statement, it does not allow the trigger to access all rows modified by the statement. This capability is planned for a future release." I wonder if that means that I can specify FOR EACH STATEMENT and have it compile fine but it seems like that I can't acccess new and old though still in 7.4. I'll have to experiment with what you suggested and perhaps look into upgrading to 7.4 as well. Thanks, Clint ----Original Message Follows---- From: Tom Lane <tgl@sss.pgh.pa.us> To: cstotesbery@acm.org CC: pgsql-sql@postgresql.org Subject: Re: [SQL] trigger conversion advice needed Date: Wed, 26 Nov 2003 10:40:08 -0500 Received: from alias2.acm.org ([199.222.69.92]) by mc11-f24.hotmail.com with Microsoft SMTPSVC(5.0.2195.6713); Wed, 26 Nov 2003 07:40:10 -0800 Received: from sss.pgh.pa.us ([192.204.191.242]) by alias2.acm.org (ACM Email Forwarding Service) with ESMTP id CRY73883 for <cstotesbery@acm.org>; Wed, 26 Nov 2003 10:40:10 -0500 Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])by sss.pgh.pa.us (8.12.10/8.12.10) with ESMTP id hAQFe819015058;Wed, 26 Nov 2003 10:40:08 -0500 (EST) X-Message-Info: JGTYoYF78jE74k1WFZAS8n73gEHv7D0r In-reply-to: <BAY9-F11pKkVavr8nCy0001de1f@hotmail.com> References: <BAY9-F11pKkVavr8nCy0001de1f@hotmail.com> Comments: In-reply-to "Clint Stotesbery" <cstotes@hotmail.com>message dated "Wed, 26 Nov 2003 11:51:42 +0000" Message-ID: <15057.1069861208@sss.pgh.pa.us> Return-Path: tgl@sss.pgh.pa.us X-OriginalArrivalTime: 26 Nov 2003 15:40:10.0631 (UTC) FILETIME=[936E3170:01C3B433] "Clint Stotesbery" <cstotes@hotmail.com> writes:> I'm working on converting a simple trigger from Oracle to Postgres andI> have a couple ofl questions that I need some help on please. First here's> the Oracle trigger: > CREATE OR REPLACE TRIGGER t_ship_date> AFTER UPDATE OR INSERT OF order_date ON orders> BEGIN> UPDATE orders> SETship_date = working_5days(order_date);> END; It looks to me like this trigger implicitly assumes that an UPDATE command would only affect the row it was fired for --- which is not at all how Postgres will interpret such a command. (Alternatively, maybe the trigger actually does result in recomputing every row's ship_date? You would only notice if ship_date had been changed manually in some rows to be different from order_date + 5...) Guessing at what is actually wanted here, my inclination would be to use a BEFORE INSERT OR UPDATE trigger and to detect updates by change from OLD to NEW. The INSERT case would simply do NEW.ship_date := working_5days(NEW.order_date);RETURN NEW; The UPDATE case would look like IF NEW.order_date <> OLD.order_date THEN NEW.ship_date := working_5days(NEW.order_date);END IF;RETURN NEW; Pretty simple when you get the hang of it. > CREATE TRIGGER t_ship_date AFTER UPDATE OR INSERT ON orders> EXECUTE PROCEDURE t_ship_date(); > I always get a parse error at or near execute. You need to say FOR EACH ROW in there too. regards, tom lane _________________________________________________________________ Set yourself up for fun at home! Get tips on home entertainment equipment, video game reviews, and more here. http://special.msn.com/home/homeent.armx
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