Re: Wrong results using decode when db upgraded to 9205

On 05/05/2004 01:05:02 PM, Daniel Fink wrote:
> Contrary to rumor, the RBO is alive and well in 10g (though
> supposed to be on it's last legs).

Well, it is alive, but not well. If you don't change defaults, 10g does dynamic sampling all by itself and you will always get some statistics. which means that you will always get CBO, unless you reset dynamic sampling and disable statistics collection with dbms_scheduler.disable('GATHER_STATS_JOB') DBMS_SCHEDULER is DBMS_JOB on steroids. Also, you cannot set optimizer_mode to rule in init.ora (OK, OK, it's spfile.ora), there is no /*+ RULE */ hint and oracle did everything to make the use of RBO as inconvenient as possible. Also, there is no documentation, so I don't know whether RBO will prune partitions, do hash joins or perform an index skip-search (OK, I know that RBO will not do thiat, but not from 10g documentation). Fortunately, the event 10053 still works as it is supposed to, so we can take a peek under the hood.

-- 
Mladen Gogala
Oracle DBA



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