Optimizer and function returning setof int4

Hi!

create table foo (
id int4 primary key,
....
);

create function bar
returns setof int4
langauge 'C'
as '...'
immutable strict
;

So query:
select foo.* from foo, bar() as b where foo.id=b;

Function foo() always returns ordered values and after first call it knows exact
number of results. It seems to me this information may be helpful for query
optimizer, so, is there way to say it to optimizer?

--
Teodor Sigaev E-mail: teodor@sigaev.ru