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Re: query_rewrite_enabled parameter

From: The Boss <usenet_at_No.Spam.Please.invalid>
Date: Thu, 14 Jun 2007 21:47:31 +0200
Message-ID: <46719b58$0$321$e4fe514c@news.xs4all.nl>


zigzagdna_at_yahoo.com wrote:
> On Jun 14, 2:30 pm, "fitzjarr..._at_cox.net" <fitzjarr..._at_cox.net> wrote:
>> On Jun 14, 1:10 pm, zigzag..._at_yahoo.com wrote:
>>
>>> I am not using function based indexes or materialized views. If I
>>> set this parameter=FALSE, will cost optimzer do something?. What
>>> are the advantages of setting this parameter
>>> Query_rewtite_enabled=TRUE.
>>
>> Give us the release of Oracle you're using and we can tell you. I
>> can tell you that from 8.1.6 onwards query_rewrite_enabled is no
>> longer necessary when using function-based indexes. From 8.1.6
>> through
>> 9.2.0.8 setting that parameter to TRUE changes the rules for
>> transitive closure (this is fixed in 10g) causing the estimated
>> cardinality for affected queries, and thus the execution plans, to be
>> incorrect.
>>
>> Post the release of Oracle you're using, to four numbers (8i, 9i, 10g
>> are not proper responses). You'll get an accurate answer after you
>> do so.
>>
>> David Fitzjarrell
>
> Sorry, I am using Oracle 9.2.0.6 on Windows 2003.

Here's a good blog on the transitive closure issue mentioned by David: http://jaffardba.blogspot.com/2006/03/transitive-closure-behaviour-when.html

-- 
Jeroen 
Received on Thu Jun 14 2007 - 14:47:31 CDT

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