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