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Re: CBO question ?

From: Ram K <lambu999_at_gmail.com>
Date: Thu, 2 Mar 2006 15:46:06 -0500
Message-ID: <db3c8dbf0603021246p54c6651di4a8a1c97ab95eca1@mail.gmail.com>


If Oracle is going to use CBO for partitioned tables by default, how does it work in the case of absence of statistics? Does it collect statistics at runtime? Usually partitioned tables tend to be big. I am interested to know how it works. Thanks.

Ram.

On 3/2/06, Bobak, Mark <Mark.Bobak_at_il.proquest.com> wrote:
>
> There can be other triggers too:
> CHOOSE will use CBO if *any* one of these is true:
> - At least one table in the query has statistics
> - A table has CBO-only characteristics:
> - table is an IOT
> - table is partitioned
> - table has parallel degree greater than 1
>
> Also, there may be other triggering events that invoke CBO.....
>
> -Mark
>
>
> *--*
> *Mark J. Bobak*
> *Senior Oracle Architect*
> *ProQuest Information & Learning*
>
> "Exception: Some dividends may be reported as qualified dividends but are
> not qualified dividends. These include:
>
> Dividends you received on any share of stock that you held for less than
> 61 days during the 121-day period that began 60 days before the ex-dividend
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>
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>
>
> ------------------------------
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *Igor Neyman
> *Sent:* Thursday, March 02, 2006 11:47 AM
> *To:* Venu.Andem_at_landregistry.gsi.gov.uk; oracle-l_at_freelists.org
> *Subject:* RE: CBO question ?
>
>
> You are wrong.
>
> Igor
>
> ------------------------------
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *Andem, Venu
> *Sent:* Thursday, March 02, 2006 11:41 AM
> *To:* oracle-l_at_freelists.org
> *Subject:* RE: CBO question ?
>
> Paul,
>
> I think its the other way round, if one of the tables in the query does
> not contain statistics then Oracle uses RBO. pls correct me if i am wrong.
>
> Venu
>
> -----Original Message-----
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org]*On Behalf Of *Baumgartel, Paul
> *Sent:* 02 March 2006 15:31
> *To:* oracle-l_at_freelists.org
> *Subject:* RE: CBO question ?
>
> If any table mentioned in the query has statistics stored in the data
> dictionary, Oracle will use the CBO.
>
>
> *Paul Baumgartel*
> paul.baumgartel_at_credit-suisse.com
> 212.538.1143
>
> -----Original Message-----
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org]*On Behalf Of *Savio Pinto (s)
> *Sent:* Thursday, March 02, 2006 10:28 AM
> *To:* oracle-l_at_freelists.org
> *Subject:* CBO question ?
>
> Hi,
>
> The execution plan for a query in oracle 9i shows "Optimizer= CHOOSE", how
> can i force the DB engine to use the COST based optimization for a query ?
>
> Oracle version is 9.2.0.4.0
>
> Thanks
> Savio Pinto
>
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--
Thanks,
Ram.

--
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Received on Thu Mar 02 2006 - 14:46:06 CST

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