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From: Marc Cousin <cousinmarc@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: inheritance: planning time vs children number vs column number
Date: Tue, 1 Mar 2011 16:39:19 +0100
Message-ID: <201103011639.19396.cousinmarc@gmail.com> (raw)
In-Reply-To: <17604.1298993631@sss.pgh.pa.us>
References: <201102281038.04945.cousinmarc@gmail.com>
	<201103010842.42128.cousinmarc@gmail.com>
	<17604.1298993631@sss.pgh.pa.us>

The Tuesday 01 March 2011 16:33:51, Tom Lane wrote :
> Marc Cousin <cousinmarc@gmail.com> writes:
> > Le mardi 01 mars 2011 07:20:19, Tom Lane a écrit :
> >> It's worth pointing out that the only reason this effect is dominating
> >> the runtime is that you don't have any statistics for these toy test
> >> tables.  If you did, the cycles spent using those entries would dwarf
> >> the lookup costs, I think.  So it's hard to get excited about doing
> >> anything based on this test case --- it's likely the bottleneck would be
> >> somewhere else entirely if you'd bothered to load up some data.
> > 
> > Yes, for the same test case, with a bit of data in every partition and
> > statistics up to date, planning time goes from 20 seconds to 125ms for
> > the 600 children/1000 columns case. Which is of course more than
> > acceptable.
> 
> [ scratches head ... ]  Actually, I was expecting the runtime to go up
> not down.  Maybe there's something else strange going on here.
> 
> 			regards, tom lane

Then, what can I do to help ?

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