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From welp <peter.wel...@trivadis.com>
Subject Re: JDBC sampler overhead and the number of records returned
Date Tue, 04 Aug 2009 12:26:56 GMT


sebb-2-2 wrote:
> 
> On 04/08/2009, welp <peter.welker@trivadis.com> wrote:
>>
>>  Thanks!
>>
>>  However, I could think of limiting the JDBC Sampler resultset looping to
>> 500
>>  records (limiting the SQL itself is not possible since some Query
>> Optimizer
>>  know to take advantage from this and choose an unadequate execution
>> plan). I
> 
> Would the Quey Optimizer change the plan if you changed the query to
> return a count of the number of records instead?
> 
>>  could live with checking the first 500 records for example and then just
>>  close the resultset as if it was completed.
>>
>>  Any hint where and how I can change this behaviour e.g. by creating an
>>  derived JDBC Sampler "JDBC Sampler Max 500"?
> 
> You can just update the existing sampler code.
> E.g. add a 'max results' variable to the GUI (or use a property for
> simplicity) and plug that into the retrieval loop.
> 
>>  Thanks a lot in advance and Regards
>>  Peter
>>
> 

Hi,

starting with Oracle 10g, yes, the Query Optimizer is aware of a "ROWNUM <=
100" filter and may adjust the plan (there is a workaround with inline views
and hints but this is a mess and quite intransparent). However, I just
changed the JDBCSampler class (parallel to your suggestion) and it works.
That's OK for me.

Thanks and Regards,
Peter

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