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Re: Guide to Posting Slow Query Questions

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Ants Aasma <ants(at)cybertec(dot)at>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Guide to Posting Slow Query Questions
Date: 2012-09-26 20:11:49
Message-ID: CAMkU=1xekNuoVp5oQSdTdaBY9g0nOLmM7D8Q97CneM4kp5Pm6A@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, Sep 12, 2012 at 11:40 PM, Ants Aasma <ants(at)cybertec(dot)at> wrote:
> On Wed, Sep 12, 2012 at 7:00 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>> Regarding the wiki page on reporting slow queries:
>> We currently recommend EXPLAIN ANALYZE over just EXPLAIN.  Should we
>> recommend EXPLAIN (ANALYZE, BUFFERS) instead?  I know I very often
>> wish I could see that data.  I don't think turning buffer accounting
>> on adds much cost over a mere ANALYZE.
>
> Given the amount of version 8 installs out there the recommendation
> should be qualified with version >9.0. Otherwise a strong +1

Edit made.

>
>> Also, an additional thing that would be nice for people to report is
>> whether long running queries are CPU bound or IO bound.  Should we add
>> that recommendation with links to how to do that in a couple OS, say,
>> Linux and Windows.  If so, does anyone know of good links that explain
>> it for those OS?
>
> I don't have any links for OS level monitoring, but with version 9.2
> track_io_timing would do the job.

I don't know how to advice people on how to use this to obtain
information on a specific query.  Would someone else like to take a
stab at explaining that?

Thanks,

Jeff


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