Re: plpgsql: defuault parameters and constant function parameters

"Roger Moloney" <ramoloney(at)hotmail(dot)com> writes:
> Having just done the first draft of a large migration from informix to
> postgres, I wanted to point out that the migration was hugely complicated by
> postgres inability to define default parameters

You can get that effect using function name overloading. For instance

create function f(x int, y int) ...

create function f(x int) ... as 'select f(x, 1)' ...

It's easier if the defaultable parameters are at the end, but I rather
wonder how your informix system is disambiguating the calls either
with a signature like that. If you leave off just one of the two
defaultable parameters, how does it know which?

> I dont want to make them output parameters as they are not output
> parameters. I am returning different output parameters. However it would be
> great if I could modify (and not pass back) the value of a input parameter.

Just use a differently named local variable, perhaps? Actually, because
of the scoping rules it seems to me to work fine even if they have the
same name:

regression=# create function ff(f1 int) returns int as $$
declare f1 int := coalesce(f1, 1);
begin
return f1;
end$$ language plpgsql;
CREATE FUNCTION
regression=# select ff(3);
ff
----
3
(1 row)

regression=# select ff(null);
ff
----
1
(1 row)

> Any chance of allowing input parameters to be modified within the function
> body ?

That check is there to prevent mistakes, and I think it's a good one.

regards, tom lane