Re: Simple postgresql.conf wizard

Mark Wong wrote:
> On Thu, Nov 13, 2008 at 11:53 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
> >> A lot of people have suggested raising our default_statistics target,
> >> and it has been rejected because there's some O(n^2) behavior in the
> >> planner, and it makes ANALYZE slower, but it's not that crazy.
> >
> > I think everyone agrees it ought to be raised.  Where the rubber meets
> > the road is deciding just *what* to raise it to.  We've got no
> > convincing evidence in favor of any particular value.
> >
> > If someone actually wanted to put some effort into this, I'd suggest
> > taking some reasonably complex benchmark (maybe TPCH or one of the DBT
> > series) and plotting planner runtime for each query as a function of
> > statistics_target, taking care to mark the breakpoints where it shifted
> > to a better (or worse?) plan due to having better stats.
> 
> Almost there...  I have a MSA70 plugged into the DL380 I have from HP
> and I'm trying to find time to get my scripts updated to deal with how
> tools have changed over the years...  I'm updating the DBT-2 (tpc-c
> kit) I have first

Yes, please test something.  I am tired if us saying we need to increase
default_statistics_target, but because we don't know the magic number,
we do nothing release after release.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +