From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Peter Childs <peterachilds(at)gmail(dot)com>, Postgresql Performance <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Commit takes a long time. |
Date: | 2008-01-04 10:17:17 |
Message-ID: | 1199441837.18598.18.camel@ebony.site |
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Lists: | pgsql-performance |
On Thu, 2008-01-03 at 11:35 -0500, Tom Lane wrote:
> "Peter Childs" <peterachilds(at)gmail(dot)com> writes:
> > Using Postgresql 8.1.10 every so often I get a transaction that takes a
> > while to commit.
>
> > I log everything that takes over 500ms and quite reguallly it says things
> > like
>
> > 707.036 ms statement: COMMIT
>
> AFAIK there are only two likely explanations for that:
>
> 1. You have a lot of deferred triggers that have to run at COMMIT time.
>
> 2. The disk system gets so bottlenecked that fsync'ing the commit record
> takes a long time.
I've seen 3 other reasons for this in the field while tuning people's
systems. In 8.3 we've fixed one, reduced the other and the third is
amenable to tuning via wal_buffers even in 8.1
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com
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