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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Changes to RULE based optimizer between Oracle8 and 9i
I guess I didn't explain very well. The query does not use IOT's It's the
same "regular" tables. In one case, it just selects from a single table with
about 11 million rows, returning about 1000, and executes for an hour. I'm
still interpreting the trace data to see exactly what it's doing, but my
question here is "why is it doing it differently?".
And sorry about the wrong list. I meant to send it to the new one.
> Keith,
>
> 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.
>
> -Mark
>
> PS fatcity is going away, use freelists.org!
>
>
> 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
> Walpole
>
> -----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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