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