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Re: Stats collector performance improvement

From: Greg Stark <gsstark(at)mit(dot)edu>
To: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Stats collector performance improvement
Date: 2006-01-03 23:28:34
Message-ID: 878xtw6gd9.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patchespgsql-performance
"Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:

> I would argue that minutes is too long, but of course this could be
> user-adjustable. I suspect that even waiting just a second could be a
> huge win, since this only matters if you're executing a lot of
> statements and you won't be doing that if those statements are taking
> more than a second or two to execute.

That's not necessarily true at all. You could just as easily have a
performance problem caused by a quick statement that is being executed many
times as a slow statement that is being executed few times.

That is, you could be executing dozens of queries that take seconds or minutes
once a second but none of those might be the problem. The problem might be the
query that's taking only 300ms that you're executing hundreds of of times a
minute.

Moreover, if you're not gathering stats for queries that are fast then how
will you know whether they're performing properly when you look at them when
they do show up?

-- 
greg


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