Clusters and CBO

From: Jonathan Bliss <bliss_jonathan_at_nossspam.hotmail.com>
Date: Wed, 31 Jul 2002 15:14:28 +0100
Message-ID: <vcS19.2148$sH3.63606@newsfep1-win.server.ntli.net>

I am working with an application originally written in Oracle 6. A major set of reference tables are built as a cluster. These reference tables are highly normalized and self referencing. i.e. an item in the main table can be related to other items in the same table that can be in turn related to others. The application appears to run more slowly with the CBO than with the rule based optimizer thus the live environment uses the RBO. The culprit appears to be when multiple aliases of the reference tables are used. The entire application is written in PL\SQL. I didn't write it.

Should the CBO *always* outperform the RBO.
Are clusters one instance this may not be the case.
Is Oracle really going to take away the RBO

Tests suggest that rebuilding the tables without the cluster, computing stats and using CBO may not degrade performance but it takes courage to bite the bullet with the live system.

Any thoughts appreciated.

Jonathan Received on Wed Jul 31 2002 - 09:14:28 CDT