Re: change_varattnos_of_a_node versus whole-row Vars

I wrote:
> change_varattnos_of_a_node(), which is used to adjust expressions
> referencing a parent relation or LIKE source relation to refer to the
> child relation, ignores whole-row Vars (those with attnum zero).
> ...
> My inclination, especially in the back branches, is to just throw error
> if we find a whole-row Var.
> ...
> There are a bunch of other things I don't like about
> change_varattnos_of_a_node, starting with the name, but those gripes are
> in the nature of cosmetics or inadequate error checking and wouldn't
> have any user-visible impact if changed.

Attached is a draft patch that adds error reports for whole-row Vars
and replaces change_varattnos_of_a_node with a more robust function.
The latter makes it kind of a large patch, but it's difficult to make
it a whole lot simpler unless we are willing to have the error messages
say only "cannot convert whole-row table reference", without any
indication of where the problem is. That seems a tad unfriendly to me.

Comments?

regards, tom lane