| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Matthew Wakeling <matthew(at)flymine(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: plpgsql arrays |
| Date: | 2009-04-03 17:30:39 |
| Message-ID: | 1238779839.5444.220.camel@ebony.2ndQuadrant |
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| Thread: | |
| Lists: | pgsql-performance |
On Fri, 2009-04-03 at 10:04 -0400, Tom Lane wrote:
> Matthew Wakeling <matthew(at)flymine(dot)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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