Re: proposal: generic function, constructor function

"Pavel Stehule" <pavel.stehule@gmail.com> writes:
> On 18/01/2008, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Can't you do that already with ANYELEMENT, or at the worst ANY?

> I would to have independent parameters and move type checking to
> function.

Okay, then you want ANY.

> Then I don't need register function exactly and then I can
> have different numbers of arguments.

The different-numbers-of-arguments bit is what I'm objecting to.
Just register the function as foo(ANY), foo(ANY,ANY), foo(ANY,ANY,ANY),
etc, and you're done without breaking anything else.

> we can use partial unique index, if it is possible - I didn't test it.

It's not --- partial indexes on system catalogs are not supported, and
pg_proc is certainly one catalog that that restriction will never be
relaxed for.  (How you going to execute a predicate without doing
function lookups?)  I don't believe that the constraint could be
expressed as a partial index predicate anyway --- how will you say
that foo(...) and foo(int) conflict, but foo(int) and foo(int,int)
don't?
        regards, tom lane