Re: vacuum and row type

I wrote:
> What I was thinking last night is that it'd be smart to move all this
> logic into the typcache, instead of repeating all the work each time we
> make the check.

Attached is a proposed patch that does it that way. I haven't finished
poking around to see if there are any other places besides
get_sort_group_operators where there is now-redundant code, but this
does pass regression tests.

Although this is arguably a bug fix, I'm not sure whether to back-patch
it. Given the lack of field complaints, it may not be worth taking any
risk for. Thoughts?

regards, tom lane