On Mon, Aug 27, 2012 at 04:03:05PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > On Fri, Feb 17, 2012 at 02:52:20PM -0500, Robert Haas wrote:
> >> Come on, really? Note that the above example works without casts if
> >> you use int *or* bigint *or* numeric, but not smallint. That could be
> >> fixed by causing sufficiently-small integers to lex as smallints,
>
> > Is there any general interest in adjusting smallint casting?
>
> We tried that once, years ago, and it was a miserable failure: it opened
> up far too many ambiguities, eg should "int4col + 1" invoke int4pl or
> int42pl? (That particular case works, because there's an exact match
> to int42pl, but we found an awful lot of cases where the parser couldn't
> resolve a best choice. IIRC there were dozens of failures in the
> regression tests then, and there would be more now.)
>
> There's also the problem that if "2 + 2" starts getting parsed as
> smallint int2pl smallint, cases like "20000 + 20000" will overflow when
> they didn't before. IMO smallint is a bit too narrow to be a useful
> general-purpose integer type, so we'd end up wanting int2pl to yield
> int4 to avoid unexpected overflows --- and that opens up more cans of
> worms, like which version of f() gets called for f(2+2).
>
> It's conceivable that a change in the lexer behavior combined with a
> massive reorganization of the integer-related operators would bring us
> to a nicer place than where we are now. But it'd be a lot of work for
> dubious reward, and it would almost certainly generate a pile of
> application compatibility problems.
>
> Some history:
> http://archives.postgresql.org/pgsql-hackers/2002-11/msg00468.php
> http://archives.postgresql.org/pgsql-hackers/2010-09/msg00223.php
> (A lot of the specific details in the 2002 thread are obsolete now,
> but the general point remains, I fear.)
Thanks, just asking. Odd int2 is so much harder than int8/numberic
casts.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ It's impossible for everything to be true. +