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Re: Slow INSERT

From: Michal Taborsky <michal(at)taborsky(dot)cz>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Slow INSERT
Date: 2004-06-29 15:47:32
Message-ID: 40E18F14.4000600@taborsky.cz (view raw or flat)
Thread:
Lists: pgsql-performance
Tom Lane wrote:
> Actually, the simpler theory is that the slowdown is caused by
> background checkpoint operations.  Now a checkpoint would slow
> *everything* down not only this one insert, so maybe that's not
> the right answer either, but it's my next idea.  You could check
> this to some extent by manually issuing a CHECKPOINT command and
> seeing if you get an insert hiccup.  Note though that closely
> spaced checkpoints will have less effect, because less I/O will
> be triggered when not much has changed since the last one.  So
> you'd want to wait a bit between experiments.

Aha! This is really the case. I've let the test run and issued manual 
CHECKPOINT command. The command itself took about 3 secs and during that 
time I had some slow INSERTS. So we know the reason.

I've read the discussion in "Trying to minimize the impact of 
checkpoints" thread and I get it, that there is nothing I can do about 
it. Well, we'll have to live with that, at least until 7.5.

Thanks of the help all the same.

-- 
Michal Taborsky
http://www.taborsky.cz


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