RE: The CBO Lie Detector

No I don't think it's doing that.... yet.  

There was (and I assume still is, I left oracle almost a year ago) a buzz inside Oracle land about doing that, but I don't think it has happened quite yet. Lots of folks recognize that doing that Oracle could "learn" to make better and better plans. Implementation of this idea has apparently been more difficult then many folks thought. So, as far as I know, it's still not there.  

Ric Van Dyke

Hotsos Enterprises

Cell 248-705-0624

Hotsos Symposium March 4-8, 2007. Be there.

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Schultz, Charles Sent: Friday, May 19, 2006 9:15 AM
To: oracle-l_at_freelists.org
Subject: The CBO Lie Detector  

After reading Jonathan Lewis's books, Tom Kyte's posts and Joze Senegacnik's presentations (and so many others out there who have contributed), one message (among others) has been beaten into my head; give the CBO all the facts, and the CBO will make the best choice. The corollary is that if you lie to the CBO, it may (or may not) come up with a sub-optimal plan.

So with all the automated features and collections in 10g, could not the engine determine if it was being lied to by comparing the estimated costs & cardinality to the actual end values? With all this talk about
"self-tuning", I would almost expect the database to come back and say
"Hey, you fed me false information!". At the very least. The next step
would be for the engine to go back and correct that false information.

Maybe the database already does this and I am missing it somehow. If so, please correct me.

charles schultz
oracle dba
aits - adsd
university of illinois  

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