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Re: Inconsistent performance

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: Joseph Bove <jbove(at)vetstar(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Inconsistent performance
Date: 2003-09-15 21:42:28
Message-ID: 20030915214228.GA17642@wolff.to (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Sep 15, 2003 at 17:34:12 -0400,
  Joseph Bove <jbove(at)vetstar(dot)com> wrote:
> 
> I do a rather simple query: select count (*) from large-table where column 
> = some value;
> 
> About 80% of the time, the response time is sub-second. However, at 10% of 
> the time, the response time is 5 - 10 seconds.
> 
> This is nothing readily apparent at the system level that comes close to 
> explaining the performance hits. CPU and memory usage (as measured by top) 
> appear to be fine.
> 
> Although there are certain tuning issues within the database itself, no 
> documentation I have seen seems to indicate that tuning issues would lead 
> to such inconsistent response time.

Looking at the output from explain analyze for the query would be useful.
It may be that there are a lot of rows that have the value in the problem
queries.

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