Re: filtering after join

Sorry for the confusion. This is what i meant. Thanks, Michael.

select *
from (select * from A, B where A.a = B.b) as s
where foo(s) < 2;

On 1/25/06, Peter Eisentraut <peter_e@gmx.net> wrote:
> andrew wrote:
> > I want to use a UDF to filter tuples t that are generated after a
> > join. More specifially, I have a UDF foo(record), which computes a
> > value for a given tuple.  I can do the filtering before the join.
> > e.g.:
> >
> > select * from A, B where foo(A)<2 and A.a=B.b;
>
> What makes you think that the filtering happens before the join here?
> And why would it matter?  The results should be all the same.
>
> --
> Peter Eisentraut
> http://developer.postgresql.org/~petere/
>


--
andrew