RE: Changes to RULE based optimizer between Oracle8 and 9i

  • From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
  • To: <ORACLE-L@xxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 30 Jan 2004 12:08:19 -0500

To my knowledge, RBO has not changed.  That includes NOT dealing w/ IOT.
So, I think if you execute a query that references an IOT, you'll
implicitly invoke the CBO.  That would explain why the plan is changing.
So, did you change a table from heap to IOT when you moved to 9i?  If
so, that's what's invoking CBO.
PS  fatcity is going away, use!
Mark J. Bobak 
Oracle DBA 
ProQuest Company 
Ann Arbor, MI 
"Imagination was given to man to compensate him for what he is not, and
a sense of humor was provided to console him for what he is."  --Horace

        -----Original Message-----
        From: Keith Moore [mailto:kmoore7@xxxxxxxxxxxx] 
        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

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