Re: factorial function/phase out postfix operators?

I wrote:
> However, we do have to have a benefit to show those people whose
> queries we break. Hence my insistence on having a working AS fix
> (or some other benefit) before not after.

I experimented with this a bit more, and came up with the attached.
It's not a working patch, just a set of grammar changes that Bison
is happy with. (Getting to a working patch would require fixing the
various build infrastructure that knows about the keyword classification,
which seems straightforward but tedious.)

As Robert theorized, it works to move a fairly-small number of unreserved
keywords into a new slightly-reserved category. However, as the patch
stands, only the remaining fully-unreserved keywords can be used as bare
column labels. I'd hoped to be able to also use col_name keywords in that
way (which'd make the set of legal bare column labels mostly the same as
ColId). The col_name keywords that cause problems are, it appears,
only PRECISION, CHARACTER, and CHAR_P. So in principle we could move
those three into yet another keyword category and then let the remaining
col_name keywords be included in BareColLabel. I kind of think that
that's more complication than it's worth, though.

regards, tom lane