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Re: sort_mem statistics ...

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: sort_mem statistics ...
Date: 2005-10-26 21:38:22
Message-ID: 20051026213822.GH16682@pervasive.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Oct 18, 2005 at 06:15:02PM -0400, Tom Lane wrote:
> "Marc G. Fournier" <scrappy(at)postgresql(dot)org> writes:
> > do we maintain anything anywhere for this?  mainly, some way of 
> > determining # of 'sorts to disk' vs 'sort in memory', to determine whether 
> > or not sort_mem is set to a good value?
> 
> As of 8.1 you could turn on trace_sort to collect some data about this.

While trace_sort is good, it doesn't really help for monitoring. What I
would find useful would be statistics along the lines of:

How many sorts have occured?
How many spilled to disk?
What's the largest amount of memory used by an in-memory sort?
What's the largest amount of memory used by an on-disk sort?
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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