From: Simon Riggs <simon@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Outer joins and equivalence
Date: Mon, 02 Jun 2008 18:10:44 +0100
Message-ID: <1212426644.4120.378.camel@ebony.site> (raw)
In-Reply-To: <14085.1211924592@sss.pgh.pa.us>
References: <1211918358.4489.257.camel@ebony.site>
<14085.1211924592@sss.pgh.pa.us>
On Tue, 2008-05-27 at 17:43 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > I have a complex query where making a small change to the SQL increases
> > run-time by > 1000 times.
>
> > The first SQL statement is of the form
>
> > A JOIN B ON (a.id = b.id) LEFT JOIN C ON (a.id = c.id)
>
> > and the second is like this
>
> > A JOIN B ON (a.id = b.id) LEFT JOIN C ON (b.id = c.id)
>
> > the only difference is the substitution of a -> b
>
> Please provide an actual test case.
Getting closer, but still not able to produce a moveable test case.
Symptoms are
* using partitioning
* when none of the partitions are excluded
* when equivalence classes ought to be able to reconcile join
Still working on it
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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To: pgsql-performance@postgresql.org
Cc: simon@2ndquadrant.com, tgl@sss.pgh.pa.us
Subject: Re: Outer joins and equivalence
In-Reply-To: <1212426644.4120.378.camel@ebony.site>
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