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Date: Sat, 1 Feb 2003 08:54:12 -0600
From: Bruno Wolff III <bruno@wolff.to>
To: pginfo <pginfo@t1.unisoftbg.com>
Cc: "pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
Subject: Re: update and IN vs. EXISTS
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On Sat, Feb 01, 2003 at 12:40:00 +0100,
  pginfo <pginfo@t1.unisoftbg.com> wrote:
> 
> If I try to execute:
>    update Table1 set fieldForUpdate = 1 where ID IN (select T2.ID from
> Table2);
> it is running very slow.

You might try:
  update Table1 set fieldForUpdate = 1 from Table2 where Table1.id = Table2.id;

This uses a nonstandard postgres extension and may not be portable, if that
is a concern.

INs are being speeded up in 7.4, so the original form might work a lot better
in the next release.