From: Tom Lane <tgl@sss.pgh.pa.us>
To: Daniel Caune <daniel.caune@ubisoft.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Strang behaviour SELECT ... LIMIT n FOR UPDATE
Date: Tue, 27 Nov 2007 23:46:29 -0500
Message-ID: <18953.1196225189@sss.pgh.pa.us> (raw)
In-Reply-To: <1E293D3FF63A3740B10AD5AAD88535D2068A6247@UBIMAIL1.ubisoft.org>
References: <1E293D3FF63A3740B10AD5AAD88535D2068A6247@UBIMAIL1.ubisoft.org>
"Daniel Caune" <daniel.caune@ubisoft.com> writes:
> I'm facing a strange behaviour with a statement SELECT ... LIMIT n FOR
> UPDATE in PostgreSQL 8.1. The number of rows returned is actually (n -
> 1). I'm trying to find whether this is an identified issue with
> PostgreSQL 8.1 that might have been fixed in a later version such as
> 8.2; I don't have any problem in moving to a later version if needed.
There's no known issue specifically of that form (and a quick test of
8.1 doesn't reproduce any such behavior). However, it is known and
documented that LIMIT and FOR UPDATE behave rather oddly together:
the LIMIT is applied first, which means that if FOR UPDATE rejects
any rows as being no longer up-to-date, you get fewer than the expected
number of rows out. You did not mention any concurrent activity in
your example, but I'm betting there was some ...
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, daniel.caune@ubisoft.com
Subject: Re: Strang behaviour SELECT ... LIMIT n FOR UPDATE
In-Reply-To: <18953.1196225189@sss.pgh.pa.us>
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