RE: Changes to RULE based optimizer between Oracle8 and 9i
- From: "Goulet, Dick" <DGoulet@xxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 30 Jan 2004 13:13:34 -0500
Well if optimiser_mode=3Drule with stats doesn't invoke CBO then I =
wonder why OEM is providing me with cost data??
Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA
-----Original Message-----
From: Keith Moore [mailto:kmoore7@xxxxxxxxxxxx]
Sent: Friday, January 30, 2004 12:59 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Changes to RULE based optimizer between Oracle8 and 9i
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We tried both queries with and without statistics. Same results.
Are you sure about OPIMIZER_MODE=3DRULE invoking the CBO if there are =
statistics. The Reference manual says otherwise (not that it's never =
been wrong).
----- Original Message -----=20
From: Goulet, Dick=20
To: Multiple recipients of list ORACLE-L=20
Sent: Friday, January 30, 2004 11:39 AM
Subject: RE: Changes to RULE based optimizer between Oracle8 and 9i
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=3DRULE will invoke the CBO.
Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA=20
-----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=3DRULE 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@xxxxxxxxxxxx
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