Oracle-L: RE: Cost vs Rule

From: Craig Munday <Craig.Munday_at_ecard.com.au>
Date: Wed, 13 Mar 2002 19:58:22 -0800
Message-ID: <F001.00428A3C.20020313195822@fatcity.com>

Bill,

If you really want to use CBO I would have thought that the plan stability features of Oracle would be sufficient to squash any argument about predictability. I have not used these myself, but they seem to have been included because of the need to guarantee predictable performance.

Just my two cents....I find the CBO much more complex than the RBO and I find myself wondering whether dealing with the complexity is actually worth the effort when the RBO provides sufficient performance for the applications I've worked on. I tend to take the simple is best approach.

Cheers,
Craig.

-----Original Message-----
Sent: Thursday, 14 March 2002 2:08 AM
To: Multiple recipients of list ORACLE-L

yes, everything analyzed.

sr tech arch has decided he wants to use RBO due to predictability in production. not much I can do at this point, unless I can really come up with convincing stats

-----Original Message-----
Sent: Wed, March 13, 2002 6:34 AM
To: Multiple recipients of list ORACLE-L

Well, since hints are implemented within comments, I would assume that other databases would simply ignore them. If anyone has direct experience, that would be interesting. Being completely database-agnostic may play against tuning.

Just a thought. I suppose you analyzed all tables when you were testing CBO?
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Thursday, March 07, 2002 2:00 PM
To: Multiple recipients of list ORACLE-L

not much - desire is to keep sql ANSI compliant due to cross-platform issues (want to be able to run the app on multiple db's)

-----Original Message-----
Sent: Thu, March 07, 2002 2:44 PM
To: Multiple recipients of list ORACLE-L

How much have you played with Oracle Hints???

-Joe

"Magaliff, Bill" <Bill.Magaliff_at_lendware.com> wrote:
> I work in a dev shop - most of the sql is canned and pretty basic.
> We've
> been running CBO in all of our dev environments, but we have a few
> long txns
> that just take forever. At the request of some savvy developers, I
> turned
> on RBO, and it brought down execution times dramatically.
>
> I've been analyzing affected tables often (we do a lot of bulk
> load/unload
> for testing), and have played with partitioning and clustering,
> particularly
> on one table that's just a dog. CBO will always do a FTS where RBO
> uses the
> PK to retrieve data.
>
> Where to go next? I've been unable to alter the costs dramatically
> enough
> to make any real difference in execution time.
>
> thx
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Magaliff, Bill
> INET: Bill.Magaliff_at_lendware.com
>
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Author: Magaliff, Bill
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Author: Craig Munday
  INET: Craig.Munday_at_ecard.com.au

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Received on Wed Mar 13 2002 - 21:58:22 CST