Re: WIP patch for LATERAL subqueries

I wrote:
> What I'd like to do next, barring objections, is to band-aid the places
> where the planner could crash on a LATERAL query (probably just make it
> throw FEATURE_NOT_SUPPORTED errors), write some documentation, and
> then commit what I've got.  After that I can go back to improve the
> planner and work on the parser refactoring issues as separate patches.

... and done (though the pgsql-committers message seems to have got hung
up for moderation).  I put some simplistic examples into section 7.2.1.5
and the SELECT reference page ... if anybody has ideas for
more-compelling small examples, please speak up.

			regards, tom lane