Re: Strange Create Index behaviour

Gary Doades <gpd@gpdnet.co.uk>

From: Gary Doades <gpd@gpdnet.co.uk>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Date: 2006-02-15T21:34:11Z
Lists: pgsql-hackers, pgsql-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!

Regards,
Gary.