Re: I still believe CBO is better than RBO, but WTH?

From: Nuno Souto <nsouto_at_optushome.com.au.nospam>
Date: Fri, 07 Sep 2001 16:02:38 GMT
Message-ID: <3b98ee97.1629944@news>

On Fri, 7 Sep 2001 15:55:46 +0100 , Andy Johnson <AJohnson_at_Armature.com> wrote:

>
>Have you tried looking into altering the OPTIMIZER_INDEX_CACHING,
>OPTIMIZER_INDEX_COST_ADJ as they can have a negative impact on some
>queries that worked fine in earlier versions of oracle, even when using
>RBO..
>

Not in this case. The point is: the plan is the same, and the same index is being picked up by RBO and CBO. Why is the performance so different?

Those parameters can make a hash join become a nested loop, or force the use of an index instead of full scan. This is much different and much more alarming.

Obviously ORACLE has done a lot more to index traversing in queries than they have let us know. Would help if they at least explained what the hey is going on...

Cheers
Nuno Souto
nsouto_at_optushome.com.au.nospam Received on Fri Sep 07 2001 - 11:02:38 CDT