Re: type info refactoring

2010/10/31 Robert Haas <robertmhaas@gmail.com>:
> On Sun, Oct 31, 2010 at 1:01 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
>>> ... I assumed that TypeInfo would be
>>> embedded in other structs directly, rather than a pointer and palloc.
>>
>> Yeah, that would avoid the extra-pallocs complaint, although it might be
>> notationally a bit of a PITA in places like equalfuncs.c.  I think that
>> would end up needing a separate COMPARE_TYPEINFO_FIELD macro instead of
>> being able to treat it like a Node* field.
>>
>> But I'm still wondering whether it's smart to try to promote all of this
>> fundamentally-auxiliary information to first-class status.  It's really
>> unclear to me that that will end up being a net win either conceptually
>> or notationally.
>
> I think this is a chicken-and-egg problem.  Most of the things we use
> typmod for are unimportant, because typmod doesn't get propagated
> everywhere and therefore if you try to use it for anything that
> actually matters, it'll break.  And on the flip side, there's no need
> for typmod to get propagated everywhere, because it's not used for
> anything all that important.  Blah!
>

yes, there is a few good possible features that's needs a better using of typmod

a) typmod for OUT varibles
b) enhanced polymorphic types - ANYELEMENT(x)

Regards

Pavel Stehule