From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bill Moran <wmoran@collaborativefusion.com>
Cc: Albe Laurenz <laurenz.albe@wien.gv.at>
Cc: Laurent Raufaste *EXTERN* <analogue@glop.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: PG writes a lot to the disk
Date: Thu, 20 Mar 2008 11:20:39 -0400
Message-ID: <10279.1206026439@sss.pgh.pa.us> (raw)
In-Reply-To: <20080320105833.c539476d.wmoran@collaborativefusion.com>
References: <669dc9710803190418g45002e87k19cb742579c1eeac@mail.gmail.com>
<669dc9710803200348x64122249jd2ac5924d78a6da0@mail.gmail.com>
<D960CB61B694CF459DCFB4B0128514C201E66F9E@exadv11.host.magwien.gv.at>
<20080320105833.c539476d.wmoran@collaborativefusion.com>
Bill Moran <wmoran@collaborativefusion.com> writes:
> However, the part I wanted to comment on (and got busy yesterday so
> am only getting to it now) is that there's no guarantee that SELECT
> isn't modifying rows.
Another way that SELECT can cause disk writes is if it sets hint bits on
recently-committed rows. However, if the tables aren't actively being
modified any more, you'd expect that sort of activity to settle out pretty
quickly.
I concur with the temporary-file theory --- it's real hard to see how
analyzing the tables would've fixed it otherwise.
regards, tom lane
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, wmoran@collaborativefusion.com, laurenz.albe@wien.gv.at, analogue@glop.org
Subject: Re: PG writes a lot to the disk
In-Reply-To: <10279.1206026439@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox