you mentioned a design that will cripple the CBO. The one I know that is
common amongst cross platform applications is using layered complex views
going up 5-7 layers or more. Ive tested this and find the RBO to be faster.
Most of the vendors tell you to use the RBO against that design. I think
they choose it so they dont have to change their application layer when they
move from one DB to the next. They just change the view syntax.
what other designs cripple the CBO?
"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message
news:bm1qm2$ege$1$830fa79f_at_news.demon.co.uk...
>
> I think Tom Kyte may be coming from
> the direction of controlling the design
> and usage of all aspects of the system.
>
> I know several ways to design a system
> that will cripple the optimizer's ability to
> do anything intelligent - even with the
> best possible statistics you can give it.
>
> However, for a reasonably designed
> system, it is possible to get pretty close
> to that 'never'.
>
> Another thought, though, is that there
> are some 'uncosted' features in some
> releases that can only be enabled by
> hinting (e.g. unnesting in 8.1). So that's
> a reason for costing above and beyond
> the usual one of 'the optimizer is using
> the wrong path'.
>
>
> --
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
>
> One-day tutorials:
> http://www.jlcomp.demon.co.uk/tutorial.html
> ____Iceland__November (tbc)
> ____Belgium__November (EOUG event)
> ____UK_______December (UKOUG conference)
>
>
> Three-day seminar:
> see http://www.jlcomp.demon.co.uk/seminar.html
> ____USA__October
> ____UK___November
>
>
> The Co-operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
>
> "Ryan Gaffuri" <rgaffuri_at_cox.net> wrote in message
> news:1efdad5b.0310080503.12cd6fc8_at_posting.google.com...
> > Tom Kyte swears that if you properly analyze your table, the CBO is
> at
> > the point where you never need hints. I find I still need them
> > 'occasionally', though not very often.
> >
> > anyone else have opinions? anyone who beta tested 10g see an
> > improvement in the CBO? IT tends to get a little better with each
> > release.
>
>
Received on Wed Oct 08 2003 - 16:34:58 CDT
