Re: Wrong results using decode when db upgraded to 9205
- From: Mladen Gogala <mladen@xxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 5 May 2004 13:45:32 -0400
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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