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
thisinformation may be helpful for query 
 
optimizer, so, is there way to say it to optimizer?


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