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query_rewrite_enabled [message #411387]

Fri, 03 July 2009 05:57

farenheiit
Messages: 31
Registered: June 2009
Location: Paris

Member

Hi,

I'd want to know if the fact that the query_rewrite_enabled parameter is set to TRUE can explain performance query issues after a migration from 9i to 10G.

I remember reading in Gavin POWELL's book that with this parameter set to TRUE execution plans may be altered.

is this parameter realyy usefull if we don't use Materialized views ?

thanks for helping

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Re: query_rewrite_enabled [message #411405 is a reply to message #411387]

Fri, 03 July 2009 07:11

JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...

Senior Member

I believe that you used to need Query_Rewrite_Enabled for function based indexes, but I'm petty sure you don't need it for that in 10g.

As far as I know, having it set to true will only alter an execution plan if there is a materialized view that can be used in place of pat of the query.

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Re: query_rewrite_enabled [message #411416 is a reply to message #411387]

Fri, 03 July 2009 07:52

farenheiit
Messages: 31
Registered: June 2009
Location: Paris

Member

So what can explain that a query which used running very fastly in 9i, is now running very slowly in 10G? the volumetric is the same...

i've set the OPTIMIZER_FEATURES_ENABLE parameter to 9.2.0 and the SQL plan is still the same

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Re: query_rewrite_enabled [message #411439 is a reply to message #411387]

Fri, 03 July 2009 10:45

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

>So what can explain that a query which used running very fastly in 9i, is now running very slowly in 10G? the volumetric is the same...
Post EXPLAIN PLAN from both servers.

Are statistics current on V10?

[Updated on: Fri, 03 July 2009 10:46]

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Re: query_rewrite_enabled [message #411449 is a reply to message #411439]

Fri, 03 July 2009 17:44

farenheiit
Messages: 31
Registered: June 2009
Location: Paris

Member

of course, I've ever checked this point

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