Date: Sun, 08 Jun 2008 19:54:45 -0400
From: Robert Treat <xzilla@users.sourceforge.net>
Subject: Re: Overhauling GUCS
In-reply-to: <87hcc3le52.fsf@oxford.xeocode.com>
To: pgsql-hackers@postgresql.org
Cc: Gregory Stark <stark@enterprisedb.com>,
	"Joshua D. Drake" <jd@commandprompt.com>, "Tom Lane" <tgl@sss.pgh.pa.us>,
	"Peter Eisentraut" <peter_e@gmx.net>, "Greg Smith" <gsmith@gregsmith.com>,
	"Andreas Pflug" <pgadmin@pse-consulting.de>,
	"Decibel!" <decibel@decibel.org>, "Josh Berkus" <josh@agliodbs.com>
Message-id: <200806081954.46114.xzilla@users.sourceforge.net>
MIME-version: 1.0
Content-type: text/plain; charset=iso-8859-1
Content-transfer-encoding: 7bit
Content-disposition: inline
References: <48409D1E.3070208@agliodbs.com>
	<1212800891.14299.35.camel@jd-laptop>
	<87hcc3le52.fsf@oxford.xeocode.com>
User-Agent: KMail/1.9.9

On Sunday 08 June 2008 19:07:21 Gregory Stark wrote:
> "Joshua D. Drake" <jd@commandprompt.com> writes:
> > On Fri, 2008-06-06 at 20:19 -0400, Tom Lane wrote:
> >> Robert Treat <xzilla@users.sourceforge.net> writes:
> >>
> >> Actually, the reason it's still 10 is that the effort expended to get it
> >> changed has been *ZERO*.  I keep asking for someone to make some
> >> measurements, do some benchmarking, anything to make a plausible case
> >> for a specific higher value as being a reasonable place to set it.
> >>
> >> The silence has been deafening.
> >
> > Not surprising really. It is a simple adjustment to make and it also is
> > easy to spot when its a problem. However it is not trivial to test for
> > (in terms of time and effort). I know 10 is wrong and so do you. If you
> > don't I am curious why I see so many posts from you saying, "Your
> > estimates are off, what is your default_statistics_target?" with yet
> > even more responses saying, "Uhh 10."
>
> Ah, but we only ever hear about the cases where it's wrong of course. In
> other words even if we raised it to some optimal value we would still have
> precisely the same experience of seeing only posts on list about it being
> insufficient.
>

The slipside to this is that we're not trying to find the perfect setting, 
we're just trying to determine a number that will cause more benefit than 
harm compared to the number we have now. While I am sure there are cases 
where 100 is too low as well, I cannot recall ever having seen someone 
suggest lowering the default_stats_target to something less than 100.  (I 
know sit back and wait for someone to comb the archives, just to find that 1 
time). 

-- 
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL