Re: filtering after join

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/