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RE: Rule Based Optimizer

From: Goulet, Dick <DGoulet_at_vicr.com>
Date: Wed, 11 Jun 2003 13:46:42 -0700
Message-ID: <F001.005AF812.20030611125954@fatcity.com>


Peter,

        OK, It seems you got my message wrong. Truly the CBO has made matters a whole lot better, especially for someone like Me who has a lot of semi educated users creating ad-hoc queries into the database. On the other hand, CBO has on occasion done some pretty dumb things that have not added up and taken way too long. At first I thought it was a statistics thing, like stale stats, but that has turned out false. If, as Oracle should, they abandon the RBO for CBO then it needs to be more consistent in making it's choices. I have a hard time trying to explain to duhvelopers why the CBO decided on an full table scan today when it used a unique index scan yesterday.

Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA

-----Original Message-----
Sent: Wednesday, June 11, 2003 3:38 PM
To: [EMAIL PROTECTED]; Goulet, Dick

Dick

I personally think the CBO is a great optimizer even if the first versions 7.0.x,7.1.x, and 7.2 was a bit shaky When somebody say that the CBO has to get better/mature then they typically have worked with the RBO and forgot that humans has this fantastic skill of adapting to known behaviour. That is we unconscious worked as preprocessors to the RBO, by using small tricks like rearranging the from clause, adding a empty sting to the left side of a join, rearranging the order of the predicates in the where clause. Since the CBO is able to take into account so many new things (hash, direct read for sort, parallel ...) when creating a plan for a statement and most of the time do et descent job. When the CBO really F...up a simple plan for at statement we humans get annoyed and surprised over how stupid the CBO is. My experience is that if you take a 1000 Sql statement the and feed them through the CBO and the RBO (with out preprocessing) the CBO will always win or you take a 1000 Sql statement and preprocess then for the RBO and preprocess then via hints and statistics for the CBO the CBO will win :-)

That my to cent's

d, Dick wrote:

>Same here. Hopefully 10i's CBO has matured.
>
>Dick Goulet
>Senior Oracle DBA
>Oracle Certified 8i DBA
>
>-----Original Message-----
>Sent: Wednesday, June 11, 2003 1:16 PM
>To: Multiple recipients of list ORACLE-L
>
>
>I know that the CBO existed on Oracle 7.0.15 for HP-UX. I remember it well
>because we would frequently get incorrect and inconsistent results.
>Installing the 7.0.16 patch _mostly_ fixed these issues.
>
>We still had a large number of queries that we hinted to use the RBO as we
>couldn't get the desired query performance with the CBO
>
>Kevin
>
>-----Original Message-----
>Sent: Wednesday, June 11, 2003 12:55 PM
>To: Multiple recipients of list ORACLE-L
>
>
>Not true. IIRC the first Oracle version with dual optimizer mode
>was 7.1.x.
>
>Best Regards,
>K Gopalakrishnan
>
>
>
>
>-----Original Message-----
>Mercadante, Thomas F
>Sent: Wednesday, June 11, 2003 9:30 AM
>To: Multiple recipients of list ORACLE-L
>
>
>CBO was what I learned on in late version of 5.x and 6.0. It was what
>Oracle taught developers back then - with the chart showing the precedence
>of how indexes were selected for a spcific query. And how the order of the
>tables in the FROM clause was *very* important in telling the CBO how to
>operate. Of course, that was when the developers had to know everything
>about the data within all the tables to get things to work right.
>
>Tom Mercadante
>Oracle Certified Professional
>
>
>-----Original Message-----
>Sent: Wednesday, June 11, 2003 11:50 AM
>To: Multiple recipients of list ORACLE-L
>
>
> I remember CBO in 7.1.6 on AIX...
>
>RF
>
>-----Original Message-----
>To: Multiple recipients of list ORACLE-L
>Sent: 6/10/2003 6:45 PM
>
>I first saw the CBO in 1994 if IIRC.
>
>Seems to me it was introduced in 7.2.
>
>I'm sure Mogens knows for sure. :)
>
>Jared
>
>
>
>
>
>
>"Ryan" <[EMAIL PROTECTED]>
>Sent by: [EMAIL PROTECTED]
> 06/10/2003 04:19 PM
> Please respond to ORACLE-L
>
>
> To: Multiple recipients of list ORACLE-L
><[EMAIL PROTECTED]>
> cc:
> Subject: Re: Rule Based Optimizer
>
>
>there not really quitting cold turkey.... its been phased out. wasnt the
>
>CBO
>introduced in 1997? Or was it earlier than that.
>----- Original Message -----
>To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
>Sent: Tuesday, June 10, 2003 6:44 PM
>
>
>
>
>>RWB,
>>
>>I'll tell you, if KG says it about Oracle, I pretty much would go to
>>
>>
>the
>
>
>>bank with it.
>>
>>RF
>>
>>-----Original Message-----
>>To: Multiple recipients of list ORACLE-L
>>Sent: 6/10/2003 4:24 PM
>>
>>
>>Mr. Gopalakrishnan:
>>
>>How do you know this? Can anyone confirm (or deny) this? I hope it is
>>true!
>>Oracle should just quit cold turkey and not support the RULE optimizer
>>at
>>all in any future releases.
>>
>>RWB
>>
>>
>>
>========================================================================
>
>
>>====================================
>>
>>Reginald W. Bailey
>>IBM Global Services - ETS SW GDSD - Database Management
>>Your Friendly Neighborhood DBA
>>713-216-7703 (Office) 281-798-5474 (Mobile) 713-415-5410 (Pager)
>>
>>
>>
>========================================================================
>
>
>>====================================
>>
>>
>>
>>
>> [EMAIL PROTECTED]
>>
>> .com To: [EMAIL PROTECTED]
>>
>> Sent by: cc:
>>
>> [EMAIL PROTECTED] Subject: RE: Rule Based
>>Optimizer
>> ity.com
>>
>>
>>
>>
>>
>> 06/10/2003
>>
>> 12:59 PM
>>
>> Please respond
>>
>> to ORACLE-L
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>RULE optimizer will not be supported in next version.
>>But you can still use the RULE optimizer and it is
>>just a matter of official support from Oracle.
>>
>>Best Regards,
>>K Gopalakrishnan
>>
>>
>>
>>
>>-----Original Message-----
>>Goulet, Dick
>>Sent: Tuesday, June 10, 2003 10:16 AM
>>To: Multiple recipients of list ORACLE-L
>>
>>
>>There appears to be a number of folks on the list who have some
>>
>>
>insight
>
>
>>into
>>the next version of the database. I'd like to ask those folks a
>>
>>
>simple
>
>
>>question. What is the future of the Rule Based Optimizer looking
>>
>>
>like?
>
>
>>Does it die in 10i??
>>
>>Dick Goulet
>>Senior Oracle DBA
>>Oracle Certified 8i DBA
>>--
>>Please see the official ORACLE-L FAQ: http://www.orafaq.net
>>--
>>Author: Goulet, Dick
>> INET: [EMAIL PROTECTED]
>>
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>>Author: K Gopalakrishnan
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>
>
>

-- 
Peter Gram, Miracle A/S
Phone : +45 2527 7107, Fax : +45 4466 8856
mailto:[EMAIL PROTECTED] - http://MiracleAS.dk



-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Goulet, Dick
  INET: [EMAIL PROTECTED]

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Received on Wed Jun 11 2003 - 15:46:42 CDT

Original text of this message

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