Re: Optimizer

When you want to guarantee the same execution plan for a query in all cases, the rule hint is still required. If the cost based optimizer is not generating efficient plans for all volumes of data, the sql may be re-written to best use the rule based approach.

In article <958415535.8780.0.pluto.d4ee154e_at_news.demon.nl>,   "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote:
> Rule based optimization is obsolete since 7.1. It is not enhanced
 anymore,
> so no parallel query, no bitmap indexes, no hints, no nothing.
> That alone is a reason to forget about it.
> And yes you can run into wrong query plans because of 'aged'
 statistics.
>
> Hth,
>
> Sybrand Bakker, Oracle DBA
>
> Jeff Hunter <marist89_at_excite.com> schreef in berichtnieuws
> 391f5eec_at_defiant.btitelecom.net...
> > I thought I read somewhere that Rule-based optimization will be
 going away
> > in future versions... When using cost based optimization, your
 objects
 need
> > to be optimized on a regular basis.
> >
> > RL <mark_at_mark-it.demon.co.uk> wrote in message
> > news:958301705.11737.0.nnrp-14.9e9864e7_at_news.demon.co.uk...
> > > I appreciate this is probably a huge topic, but can anyone point
> > > me in the direction of information about the Oracle optimizer.
> > > In particular, what should the optimizer rule be
> > > set to (CHOOSE, RULE etc). If the optimizer is using cost
> > > based optimization, is it necessary to analyze tables regularly or
> > > can it be run once. Does the cost based optimizer always give
 better
> > > results that the rule based optimizer or are there too many
 variables
> > > to decide this.
> > >
> > > Are there are good tools to help with optimization, (where to add
> > > indexes etc), I found tkprof output very cryptic.
> > >
> > > Many thanks
> > >
> > >
> > >
> >
> >
>
>

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Before you buy. Received on Mon May 15 2000 - 00:00:00 CDT