Re: filtering after join

andrew wrote:
> 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(at)gmx(dot)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;

Note that these two queries will produce the same internal execution
plan, so if you wanted to make some difference you will not.

--
Peter Eisentraut
http://developer.postgresql.org/~petere/