Re: Cost Vs. Rules Based Optimizers

jp_at_vllyoak.resun.com (Jeff Perry) wrote:
>
> vv_at_mbunix (Vincent A Ventrone) writes:
>
> > >
> > >Has anyone done any extensive testing between the two optimizers where you
> > >have switched from running highly optimized and very large queries against a
> > >optimizer and most of them go against two entire years of sales history.
> > > (Stuff deleted...)
> > >We know there are minor differences in syntax, such as the driving table
> >
> > We haven't run tests yet, but according to the Oracle Tuning App.
> > under v 7 class (which I took last week -- and recommend) syntax
> > is supposed to have no effect on the execution plan generated by
> > the cost-based optimizer (that is, order of FROM tables and WHERE
> > clauses). Supposedly it uses only infomation generated by ANALYZE.
> >
> > Of course, the claims may be wrong....:-)
>
> We found that the cost-based optimizer caused incorrect results. Our
> applications people reported no problems after switching to the
> rules-based optimizer (7.0.13.1).
> --
> Jeff Perry
> jp%vllyoak.resun.com%blkhole_at_sdd.hp.com
>
>
There were initially some problems with the cost based optimizer, but they have long been solved. You are referring to a pretty old release (7.0.13.1).

Mark Received on Wed Jan 18 1995 - 09:56:44 CET