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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Changes to RULE based optimizer between Oracle8 and 9i
We tried both queries with and without statistics. Same results.
Are you sure about OPIMIZER_MODE=RULE invoking the CBO if there are statistics. The Reference manual says otherwise (not that it's never been wrong).
Logic says one thing, experience says another. Question one, are the tables analyzed? If so, since RBO is deprecated in 9i even setting OPTIMIZER_MODE=RULE will invoke the CBO.
Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA
-----Original Message-----
From: Keith Moore [mailto:kmoore7_at_jcpenney.com]
Sent: Friday, January 30, 2004 11:54 AM
To: Multiple recipients of list ORACLE-L
Subject: Changes to RULE based optimizer between Oracle8 and 9i
We move an application that uses OPTIMIZER_MODE=RULE from Oracle8 to 9i. Most of it is fine, but there are two queries that have a very different execution plan. In one case, the execution time increases from less than a minute to more than an hour. Neither query uses any of the new Oracle 9i features.
My understanding is that the Rule optimizer code has not changed, except to account for new features like IOT's. Has anyone else seen this type of behavior?
Keith Moore
Oracle Certified Professional
972-431-5126
kmoore7_at_jcpenney.com
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