Vik Fearing <vik@postgresfriends.org> writes:
> I'm -1 on keeping ! around as a hard-coded postfix operator.
Before we go much further on this, we should have some proof
that there's actually material benefit to be gained. I spent some
time just now trying to relax the AS restriction by ripping out
postfix ops, and the results were not too promising. Indeed the
postfix-ops problem goes away, but then you find out that SQL's
random syntax choices for type names become the stumbling block.
An example here is that given
SELECT 'foo'::character varying
it's not clear if "varying" is supposed to be part of the type name or a
column label. It looks to me like we'd have to increase the reserved-ness
of VARYING, PRECISION, and about half a dozen currently-unreserved
keywords involved in INTERVAL syntax, including such popular column names
as "month", "day", and "year".
Plus I got conflicts on WITHIN, GROUP, and FILTER from ordered-set
aggregate syntax; those are currently unreserved keywords, but they
can't be allowed as AS-less column labels.
We could possibly minimize the damage by inventing another keyword
classification besides the four we have now. Or maybe we should
think harder about using more lookahead between the lexer and grammar.
But this is going to be a lot more ticklish than I would've hoped,
and possibly not cost-free, so we might well end up never pulling
the trigger on such a change.
So right at the moment I'm agreeing with Stephen's nearby opinion:
let's not deprecate these until we've got a patch that gets some
concrete benefit from removing them.
regards, tom lane
