X-Original-To: pgsql-sql-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3384552896 for ; Tue, 19 Jul 2005 06:26:04 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 78072-03 for ; Tue, 19 Jul 2005 09:25:53 +0000 (GMT) Received: from ar-sd.net (unknown [82.77.155.72]) by svr1.postgresql.org (Postfix) with ESMTP id 4EE605281E for ; Tue, 19 Jul 2005 06:25:51 -0300 (ADT) Received: from localhost (localhost [127.0.0.1]) by ar-sd.net (Postfix) with ESMTP id 3844028BF5; Tue, 19 Jul 2005 12:17:25 +0300 (EEST) Received: from ar-sd.net ([127.0.0.1]) by localhost (linz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 15980-05; Tue, 19 Jul 2005 12:17:23 +0300 (EEST) Received: from forge (unknown [192.168.0.11]) by ar-sd.net (Postfix) with SMTP id 47CEF28BDF; Tue, 19 Jul 2005 12:17:23 +0300 (EEST) Message-ID: <01d301c58c44$25cddb80$0b00a8c0@forge> From: "Andy" To: "Richard Huxton" Cc: References: <00e001c58b93$ad30b130$0b00a8c0@forge> <42DCC3DD.5000806@archonet.com> Subject: Re: Create trigger for auto update function Date: Tue, 19 Jul 2005 12:27:54 +0300 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: by amavisd-new at ar-sd.net X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.342 tagged_above=0 required=5 tests=AWL, FORGED_RCVD_HELO X-Spam-Level: X-Archive-Number: 200507/161 X-Sequence-Number: 22139 Off topic :) I think we posted in the same time :)) ----- Original Message ----- From: "Richard Huxton" To: "Andrei Bintintan" Cc: Sent: Tuesday, July 19, 2005 12:11 PM Subject: Re: [SQL] Create trigger for auto update function > Andrei Bintintan wrote: >> >> Now, I want to write a trigger function that automatically updates the >> pass_md5 with the md5 function of the pass. I tried this: >> >> CREATE FUNCTION update_pass(integer) RETURNS integer AS $$ >> UPDATE hoy SET pass_md5=md5(pass) WHERE id=$1; >> SELECT 1; >> $$ LANGUAGE SQL; >> >> and CREATE TRIGGER triger_users_pass_md5 AFTER INSERT OR UPDATE >> ON hoy >> EXECUTE PROCEDURE update_pass(integer); > > The simplest way to do this is with a BEFORE trigger, and just modifying > the NEW pseudo-record. > > > CREATE OR REPLACE FUNCTION maintain_pass_md5() RETURNS TRIGGER AS ' > BEGIN > NEW.pass_md5 = md5(NEW.pass); > RETURN NEW; > END > ' LANGUAGE plpgsql; > > CREATE TRIGGER hoy_maintain_pass_md5 > BEFORE INSERT OR UPDATE ON hoy > FOR EACH ROW EXECUTE PROCEDURE maintain_pass_md5(); > > > Note that the function is defined to return type TRIGGER and that we > return NEW. If we returned NULL, the row would be skipped by the current > update statement. This means only one actual on-disk update takes place, > and as far as everyone is concerned pass_md5 automagically updates itself. > > If the md5() function was actually an operation that would take a long > time, it might be worth checking whether pass has been changed: > IF NEW.pass IS DISTINCT FROM OLD.pass THEN > ... > END IF > However, if you do this then you have to test TG_OP to see whether you are > inserting or updating - insert ops don't have OLD defined. > > HTH > -- > Richard Huxton > Archonet Ltd > > ---------------------------(end of broadcast)--------------------------- > TIP 6: explain analyze is your friend > >