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Message-ID: <b42b73150812170649rd0a689bw41b8215d8488f9b4@mail.gmail.com>
Date: Wed, 17 Dec 2008 09:49:26 -0500
From: "Merlin Moncure" <mmoncure@gmail.com>
To: "Jaime Casanova" <jcasanov@systemguards.com.ec>
Subject: Re: measure database contention
Cc: "psql performance list" <pgsql-performance@postgresql.org>
In-Reply-To: <3073cc9b0812161132w3ae157a8n69e2b0cccea05ca2@mail.gmail.com>
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References: <3073cc9b0812161132w3ae157a8n69e2b0cccea05ca2@mail.gmail.com>

On Tue, Dec 16, 2008 at 2:32 PM, Jaime Casanova
<jcasanov@systemguards.com.ec> wrote:
> Hi,
>
> we have a some bad queries (developers are working on that), some of
> them run in 17 secs and that is the average but when analyzing logs i
> found that from time to time some of them took upto 3 mins (the same
> query that normally runs in 17secs).
>
> so my question is: how could i look for contention problems?

Sometimes queries can have fluctuating plans.  For example this can
happen if you have sorts or hashes that are very near the allowed
limit set in work_mem.  so you want to catch it both ways via explain
analyze.

merlin