Re: Statistics and optimizer

On Tue, 08 May 2001, annmyhre_at_hotmail.com wrote:

> That really confuse me. What you say is that, if I use any
> hints exept RULE, and even though I haven't collected ANY
> statistics (there is absolutely NO statistics genererated an
> any object whatsoever), Oracle (optimizer) will choose CBO? My
> problem is that I want of course in most cases optimizer to
> choose CBO, but from the information I have got it seems that
> it will choose RBO if I haven't rembered to use ANALYZE
> first. I have tried different approches and from the EXPLAIN
> PLAN it also seems to choose CBO even though I have not used
> ANALYZE. But maybe I read something wrong?

With no hints, no analyze, and optimiser_mode of choose, you should get RBO.

http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/a76992/optimops.htm#38218

If there are hints, you can always force CBO. That is, I believe, what Ricky was referring to.

http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/a76992/optimops.htm#38289

-- 
Galen
I don't want to be the rock.  Yeah, okay, what do you want to be?
I want to be the piece of glass.