X-Original-To: pgsql-sql-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.2]) by svr1.postgresql.org (Postfix) with ESMTP id E4443D1E929 for ; Fri, 19 Mar 2004 06:22:41 +0000 (GMT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (neptune.hub.org [200.46.204.2]) (amavisd-new, port 10024) with ESMTP id 71371-02 for ; Fri, 19 Mar 2004 02:22:33 -0400 (AST) Received: from rock.spider.ru (rock.spider.ru [62.183.34.226]) by svr1.postgresql.org (Postfix) with ESMTP id 62DC7D1E7F2 for ; Fri, 19 Mar 2004 02:22:32 -0400 (AST) Received: from rock (localhost [127.0.0.1]) by rock (Postfix) with SMTP id D9E6C913EB for ; Fri, 19 Mar 2004 09:22:30 +0300 (MSK) Received: from sad.localnet.ru (sad.localnet.ru [10.0.0.33]) by rock.spider.ru (Postfix) with ESMTP id 2A6AF913EA for ; Fri, 19 Mar 2004 09:22:30 +0300 (MSK) Content-Type: text/plain; charset="iso-8859-1" From: sad Organization: IT To: pgsql-sql@postgresql.org Subject: Re: perfomance question Date: Fri, 19 Mar 2004 09:27:43 +0300 User-Agent: KMail/1.4.3 References: <200403180941.45591.sad@bankir.ru> <200403181038.30116.josh@agliodbs.com> In-Reply-To: <200403181038.30116.josh@agliodbs.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Message-Id: <200403190927.43971.sad@bankir.ru> X-Virus-Scanned: by amavisd-new at postgresql.org X-Archive-Number: 200403/196 X-Sequence-Number: 17295 On Thursday 18 March 2004 21:38, you wrote: > Sad, > > > what are perfomance difference bitween > > a) update t1 set f1 =3D 'x', f2 =3D 'y'; > > b) update t1 set f1 =3D 'x', f2 =3D f2; > > c) update t1 set f1 =3D 'x'; > > ? > > Not a lot. Why don't you try it? Really ! why ? :-) I forgot to ask the second question: How these updates affect a data storage ? (does (b) cause physical update of f2 ?)