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From Bryan Pendleton <bpendle...@amberpoint.com>
Subject Re: Few quick questions on Index, Optimizer
Date Thu, 12 Nov 2009 15:24:42 GMT
kashyup wrote:
> Hello all, after going through much docs i think i have lost answers to much
> basic questions. I would appreciate any reply...

These are quite interesting questions. It seems that you have done a lot
of research and are seeing some puzzling results.

One of the first things to check for, when you experience varying behavior
on the same queries with the same data, is whether you are getting the
same query plan each time. If you aren't, we can try to figure out what
is the "good" plan and what is the "bad" plan, and why Derby sometimes
chooses one or the other. If you are, we can diff the two plans and try
to figure out why they are not executing in roughly the same performance.

One possible explanation for counter-intuitive performance behaviors is
a lack of memory. Have you experimented with giving Derby substantially
more memory? http://db.apache.org/derby/docs/10.5/ref/rrefproper81359.html

thanks,

bryan


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