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From Rick Hillegas <rick.hille...@oracle.com>
Subject Re: Modifying "sql join" optimization algorithm in Derby
Date Fri, 10 Jun 2011 14:07:07 GMT
On 6/10/11 1:07 AM, Piumi Nanayakkara wrote:
> Hi all,
> For a research purpose I'm considering $subject when database is 
> stored in a solid state device.Can some one please clarify me the 
> packages/classes that i should study/modify for this purpose.
> Thank You!
> Best Regards,
> Piumi Nanayakkara
Hi Piumi,

Probably what is most relevant is the Cost Model for these devices. 
Derby ships with a hard-coded Cost Model for heap and index files. That 
Cost Model was tuned many years ago and probably doesn't capture the 
actual performance of modern disks. I was not part of the effort to tune 
that Cost Model so I can't give you a lot of detail here.

If you want to tweak the Cost Model to better reflect the performance of 
solid state disks, I recommend that you study the 
org.apache.derby.iapi.store.access.StoreCostController interface and its 
implementations. Unfortunately, I am not aware of any tools which will 
help you create an implementation which is tuned to the behavior of a 
particular disk. You may develop such a tool as you pursue your 
research. If so, I encourage you to donate that tool back to the 
community. I'm sure it will be useful to other researchers and developers.

Perhaps you will get more detailed advice from someone who was closer to 
the original effort which tuned the current Cost Model.

Sounds like an interesting project. Good luck!


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