Re: Collations versus record-returning functions

I wrote:
> ISTM there are basically three things we might do about this:

> (1) Decide that the patch's behavior is correct and what's embodied in
> the regression expected file is wrong.

> (2) Allow collations to propagate up through nodes that deliver
> noncollatable outputs.

> (3) Decide that composite types are collatable.

I thought of another possibility, which is to special-case field
selection from a function-returning-composite, ie make it look
through the function node and use the function's input collation.
FieldSelect needs to be a special case in the collation assignment code
anyway because of the possibility of taking the collation from the field
declaration instead of the input, so this is not *quite* as ugly as it
first sounds.  It's still ugly, but it makes that regression test pass
with only a very localized change.  So I will do it like that for now
until someone comes up with an argument for another choice.
        regards, tom lane