RE: hinting and the rule based optimizer
- From: "Powell, Mark D" <mark.powell@xxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 1 Apr 2004 15:47:04 -0500
Since version 7.3 the presence of any valid hint in the SQL statement other
than the RULE hint invoked the CBO even in the absence of statistics. If
the db is set to run rule based and there are no hints in the SQL then
generating statistics should have no effect on the existing application, but
it would provide statistics to support any hinted queries you care to
submit.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of ryan.gaffuri@xxxxxxx
Sent: Thursday, April 01, 2004 3:04 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: hinting and the rule based optimizer
We have a legacy 8.1.7.3 instance that is in RBO mode. My group does not own
it, so we cannot change it to CBO.
When I hint anything from an index to ordered, etc... it switches to the CBO
and since nothing is analyzed, it's an even worse plan... Not allowed to
analyze the tables either because it's not our property.
Any rules around hinting the RBO in 8.1.7.3? Why would it switch to the CBO
from a simple hint? I never use the RBO so please bare with me.
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