Re: PL/SQL functions in SQL where clauses - how to evaluate them as a late as possible

strange (select) statement. Can you PLEASE elaborate ?

"Ashish Mittal" <mittalashish_at_yahoo.com> wrote in message news:iTJb8.75447$AV5.376151_at_rwcrnsc51.ops.asp.att.net...
> Well, one way to have the function evaluated last would be to do
>
> select * from
> (
> select * from <tables> where <normal where clauses>
> )
> where permission_p(param_column)
>
> However, I think it is EXTREMELY rare for this to be needed. Can you
 PLEASE
> examine whether the permissions_P can be made a part of the sql. Can you
> post the full code of permissions_p
>
> Ashish
> "Dirk Gomez" <usenet_at_dirkgomez.de> wrote in message
> news:c8a033bd.0202150955.34d721bf_at_posting.google.com...
> > Hi Adrian,
> >
> > no the SQL statement in the PL/SQL function is pretty much tuned. It
> > works amazingly quick.
> >
> > What hurts is that the PL/SQL function in the where clause usually is
> > the _least_ selective predicate and I want it to be evaluated as late
> > as possible. But even when I do stuff like:
> >
> > select * from (
> > select field1, field2, expensive_sql_function(param1,param2) as
> > result
> > from ...
> > )
> > where result='t';
> >
> > the optimizer seems to rearrange my statement to compute
> > expensive_sql_function very early during the process.
> >
> > I tried "associate statistics" with high costs and/or low selectivity.
> > And I tried the ORDERED_PREDICATE hint. But both for no avail.
> >
> > cheers Dirk
>
>
Received on Sun Feb 17 2002 - 22:26:55 CET