| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
 |
 | |||
| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
|
| |||
Home -> Community -> Mailing Lists -> Oracle-L -> RE: cost
*I think*, this is due to optimizer heuristics . First_rows cost model
is implemented as an heuristics model and applied over the usual cost
comparisons. I have seen optimizer choose a costlier plan because this
heuristics was/was not applied.
I wonder what results you would get if you have optimizer_mode set to
first_rows in your test case ?
Thanks
Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Cary Millsap
Sent: Monday, April 05, 2004 12:35 PM
To: oracle-l_at_freelists.org
Subject: RE: cost
Yep, "bug" is where we're going with it... But we haven't had time yet to go into detail.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
* Nullius in verba *
Upcoming events:
- Performance Diagnosis 101: 4/6 Seattle, 5/7 Dallas, 5/18 New Jersey
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Bobak, Mark
Sent: Monday, April 05, 2004 12:24 PM
To: oracle-l_at_freelists.org
Subject: RE: cost
Hmm....I should have known, Cary...;-)
I actually had the thought, as I was typing that reply "hmm....*always*, really? Are you sure? Yeah, of course you are, if it's not always choosing the lowest cost, what else could it do....?" Of course, Oracle found a way.....
My first thought, though, would be that this is a bug.....is that where you're going with this? Or is there something more going on? Did 10053 reveal anything interesting?
-Mark
Mark J. Bobak
Oracle DBA
ProQuest Company
Ann Arbor, MI
"Post Hoc Ergo Propter Hoc"
The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. If the reader of this message is not the intended recipient, you are hereby notified that your access is unauthorized, and any review, dissemination, distribution or copying of this message including any attachments is strictly prohibited. If you are not the intended recipient, please contact the sender and delete the material from any computer.
 |
 |