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Home -> Community -> Usenet -> c.d.o.server -> Re: Why Adding "+0" Make A Query Run Faster
Hi Niall,
of course, I know that using of partition feature requires CBO. But somewhere on metalink forum I read that using of RBO possible as well, but without performance gain. This got me confused a bit.
Regards,
-- Roman Mirzaitov Brainbench MVP for Oracle Administration www.brainbench.com "Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in message news:3d11cd6a$0$8512$ed9e5944_at_reading.news.pipex.net...Received on Fri Jun 21 2002 - 00:39:18 CDT
> "Roman Mirzaitov" <rmirzaitov_at_kt.kg> wrote in message
> news:aeshkv$9ph8c$1_at_ID-127142.news.dfncis.de...
> > > a) He's not using RBO, he's using CBO (on partitioned table, that's
> > > the only way).
> > Oracle manuals says:
> > "If OPTIMIZER_MODE=CHOOSE, if statistics do not exist, and if you do not
> add
> > hints to your SQL statements, then your statements use the RBO."
> > So we don't know for sure which optimizer mode used in our case.
> > Besides, you can use RBO mode with partitioned table, you just will not
> gain
> > any performance benefits from partitioning. But you can.
>
> We do know. Its the CBO. Again from the manuals
>
> Features that Require the CBO
> The use of any of the following features requires the use of the CBO:
>
> a.. Partitioned tables
>
> b.. Index-organized tables
>
> c.. Reverse key indexes
>
> d.. Function-based indexes
>
> e.. SAMPLE clauses in a SELECT statement
>
> f.. Parallel execution and parallel DML
>
> g.. Star transformations
>
> h.. Star joins
>
> i.. Extensible optimizer
>
> j.. Query rewrite (materialized views)
>
> k.. Progress meter
>
> l.. Hash joins
>
> m.. Bitmap indexes
>
> n.. Partition views (release 7.3)
>
>
> ------------------------------------------------------------------------
> Note:
> Even if the parameter OPTIMIZER_MODE is set to RULE, the use of
> these features enables the CBO.
>
> ------------------------------------------------------------------------
>
>
>
>
> --
> Niall Litchfield
> Oracle DBA
> Audit Commission UK
> *****************************************
> Please include version and platform
> and SQL where applicable
> It makes life easier and increases the
> likelihood of a good answer
>
> ******************************************
>
>
>
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