Re: Common Table Expressions (WITH RECURSIVE) patch

Attached is the result of a couple of days hacking on the WITH RECURSIVE
patch.  This moves us a lot closer to having sanity in the parsing
phase, though I'm still quite unhappy with the second half of the
processing in parse_cte.c.  I added some infrastructure to make the
first half's search for CTE references reasonably bulletproof, but the
second half needs to be converted to use the same infrastructure, and
I didn't do that yet because I didn't understand what it was doing.
In particular, what the heck is the exception in findCteName that allows
some other CTE's non_recursive_term to be stored into the
non_recursive_term for the current one?  That seems mighty broken.

There are a number of unfinished corner cases (look for XXX in the
patch) but they aren't in the way of further progress.  The next big
thing seems to be to figure out exactly how to do multiple references
to CTE outputs, so that we can de-bogotify the planner.

            regards, tom lane