Re: Calling PrepareTempTablespaces in BufFileCreateTemp

However, by that argument we should change all 3 of these functions to
set up the data.  If we're eating the layering violation to the extent
of letting OpenTemporaryFile call into commands/tablespace, then there's
little reason for the other 2 not to do likewise.

I still remain concerned that invoking catalog lookups from fd.c is a darn
bad idea, even if we have a fallback for it to work (for some value of
"work") in non-transactional states.  It's not really hard to envision
that kind of thing leading to infinite recursion.  I think it's safe
right now, because catalog fetches shouldn't lead to any temp-file
access, but that's sort of a rickety assumption isn't it?