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Re: Strange Create Index behaviour

From: Gary Doades <gpd(at)gpdnet(dot)co(dot)uk>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Strange Create Index behaviour
Date: 2006-02-15 21:34:11
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackerspgsql-performance
Tom Lane wrote:
  > I tried forcing PG to use src/port/qsort.c on the Fedora machine,
> and lo and behold:
> 	new Fedora 4 machine: shortest 434 msec, longest 8530 msec
> So it sure looks like this script does expose a problem on BSD-derived
> qsorts.  Curiously, the case that's much the worst for me is the third
> in the script, while the shortest time is the first case, which was slow
> for Gary.  So I'd venture that the *BSD code has been tweaked somewhere
> along the way, in a manner that moves the problem around without really
> fixing it.  (Anyone want to compare the actual FreeBSD source to what
> we have?)

If I run the script again, it is not always the first case that is slow, 
it varies from run to run, which is why I repeated it quite a few times 
for the test.

Interestingly, if I don't delete the table after a run, but just drop 
and re-create the index repeatedly it stays a pretty consistent time, 
either repeatedly good or repeatedly bad!


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