From: Mark Stosberg <mark@summersault.com>
Subject: Re: How to debug performance problems
Date: Wed, 21 Feb 2007 12:49:12 -0500
Organization: Hub.Org Networking Services
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To: pgsql-performance@postgresql.org

Ray Stell wrote:
> I'd like to have a toolbox prepared for when performance goes south.
> I'm clueless.  Would someone mind providing some detail about how to
> measure these four items Craig listed:
> 
> 1. The first thing is to find out which query is taking a lot of time.
> 
> 2. A long-running transaction keeps vacuum from working.
> 
> 3. A table grows just enough to pass a threshold in the
>    planner and a drastically different plan is generated.

I just ran into a variation of this:

3.5 A table grows so large so that VACUUMING it takes extremely long,
interfering with the general performance of the system.

In our case, we think the table had about 36 million rows when it hit
that threshold.

I'm now working on a better solution for that table.

  Mark