Re: refactoring planner data structures

Neil Conway <neilc@samurai.com> writes:
> I was rather disappointed, as I wasn't able to find a clean
> way to get around the problem described in the thread above -- e.g.
> in_info_list and query tree mutators:

> http://archives.postgresql.org/pgsql-hackers/2005-03/msg00718.php

> How were you thinking of solving it?

Yeah, that gave me some headaches :-(.  It turns out that most of the
uses of walkers/mutators are on not-yet-planned Querys and so the
failure to visit the in_info_list doesn't matter.  I had to add code in
just two places to visit the in_info_list explicitly.

Plan B would be to add PlannerInfo as a node type that the
walker/mutator code knows how to traverse.  I didn't do this for the
moment because it's not immediately obvious why the traverse should only
visit the Query and the in_info_list subfields; that seems sufficiently
ad-hoc to be better kept at the call sites for the moment.  Maybe we can
revisit that later.

Ideally I'd like to get rid of in_info_list altogether ... it's a bit of
a kluge.  Don't see how to do that yet though.
        regards, tom lane