From: Simon Riggs <simon@2ndQuadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Matthew Wakeling <matthew@flymine.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: plpgsql arrays
Date: Fri, 03 Apr 2009 18:30:39 +0100
Message-ID: <1238779839.5444.220.camel@ebony.2ndQuadrant> (raw)
In-Reply-To: <28595.1238767442@sss.pgh.pa.us>
References: <alpine.DEB.2.00.0904031420470.21772@aragorn.flymine.org>
<603c8f070904030647u1c92e13ew53612ac0011ed7c1@mail.gmail.com>
<alpine.DEB.2.00.0904031455210.21772@aragorn.flymine.org>
<28595.1238767442@sss.pgh.pa.us>
On Fri, 2009-04-03 at 10:04 -0400, Tom Lane wrote:
> Matthew Wakeling <matthew@flymine.org> writes:
> > On Fri, 3 Apr 2009, Robert Haas wrote:
> >> Why not just use SQL to do the join?
>
> > Because the merge condition is:
>
> > WHERE l1.start <= l2.end AND l2.start <= l1.end
>
> > and merge joins in postgres only currently cope with the case where the
> > merge condition is an equals relationship.
(snip)
> I don't actually believe that a standard merge join algorithm will work
> with an intransitive join condition ...
I think it's a common enough problem that having a non-standard join
algorithm written for that case would be interesting indeed.
--
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, matthew@flymine.org
Subject: Re: plpgsql arrays
In-Reply-To: <1238779839.5444.220.camel@ebony.2ndQuadrant>
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