От: Michal Taborsky
Тема: Re: Slow INSERT
Дата: ,
Msg-id: 40E18F14.4000600@taborsky.cz
(см: обсуждение, исходный текст)
Ответ на: Slow INSERT  (Michal Táborský)
Ответы: Re: Slow INSERT  (Tom Lane)
Список: pgsql-performance

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Slow INSERT  (Michal Táborský, )
 Re: Slow INSERT  (Tom Lane, )
  Re: Slow INSERT  (Michal Taborsky, )
   Re: Slow INSERT  (Tom Lane, )
 Re: Slow INSERT  (Michal Taborsky, )
  Re: Slow INSERT  (Tom Lane, )

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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