Re: query_planner() API change

Robert Haas <robertmhaas@gmail.com> writes:
> On Sun, Aug 4, 2013 at 6:20 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think it's time to bite the bullet and *not* pass back completed paths.
>> What's looking more attractive now is to just pass back the top-level
>> RelOptInfo ("final_rel" in query_planner()).

> I tend to think this is a pretty good plan.

I looked around a little more and noted that this would complicate the
special-case handling of an empty join tree (viz, "SELECT 2+2").  Right
now query_planner() just has to make the appropriate Result path and it's
done.  We'd have to create a dummy RelOptInfo representing an empty set
of relations, which is a bit weird but probably not too unreasonable
when all's said and done.
        regards, tom lane