From: | "Gokulakannan Somasundaram" <gokul007(at)gmail(dot)com> |
---|---|
To: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
Cc: | "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Neil Conway" <neilc(at)samurai(dot)com>, "pgsql-hackers list" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: EXPLAIN ANALYZE printing logical and hardware I/O per-node |
Date: | 2007-12-17 07:28:33 |
Message-ID: | 9362e74e0712162328m3ea21628se928e59ea27c6747@mail.gmail.com |
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On Dec 16, 2007 1:03 AM, Heikki Linnakangas <heikki(at)enterprisedb(dot)com> wrote:
> Gokulakannan Somasundaram wrote:
> > I was going to say that I'm really only interested in physical I/O.
> Logical
> >> I/O which is satisfied by the kernel cache is only marginally
> interesting
> >> and
> >> buffer fetches from Postgres's shared buffer is entirely uninteresting
> >> from
> >> the point of view of trying to figure out what is slowing down a query.
> >
> > Ok the Physical I/Os are already visible, if you enable
> log_statement_stats.
>
> I think you missed the point. What log_statement_stats shows are not
> physical I/Os, they're read() system calls. Unfortunately there's no
> direct way to tell if a read() is satisfied from OS cache or not. Greg's
> suggestion was about how to do that.
>
Oh OK. Thanks for clarifying..
--
Thanks,
Gokul.
CertoSQL Project,
Allied Solution Group.
(www.alliedgroups.com)
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