<sweidanz_at_yahoo.com> wrote in message
news:Zryx7.10$cH1.347_at_nsw.nnrp.telstra.net...
> Can you please explain how you read it that way and how you knew its
> cost-based method? If the optimiser is CHOOSE it does not mean Oracle is
> going use the cost-based!! If none of the tables in the query is analyzed,
> oracle is going use the rule-based. right?
Of course you are right. If no stats exist then Oracle has to use the rule
based optimiser.So I should have said that stats might be "out of
date,innaccurate or non-existent". My real gripe was with the statement "I
see you are using RULE. " You could only state this for sure if the explain
plan said Optimizer=RULE. Any other value says that Oracle will use the CBO
if at all possible. Given that you will get stats for example if you do an
import then it is quite likely that stats exist (at least in any test
environment where tuning efforts are being made). If I see Optimiser mode
choose I assume that the intention is to use the cost based optimiser, and
then concentrate as you suggest on whether the stats are appropriate, or
indeed the sql.
--
Niall Litchfield
Oracle DBA
Audit Commission UK
>
>
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> I don't read it that way.
>
> from the original post
> "
> Execution Plan
> ----------------------------------------------------------
> 0 SELECT STATEMENT Optimizer=CHOOSE
> "
> This says COST based to me. Of course the stats on the tables may well be
> out of date or inaccurate.
>
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Received on Tue Oct 16 2001 - 04:47:54 CDT
