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From Bryan Pendleton <bpendleton.de...@gmail.com>
Subject Re: SQL performance with complex query
Date Sat, 17 Apr 2010 15:39:53 GMT
> I think this could be a case where the query optimizer could use some 
> work? Is it useful for me to file a bug report somewhere, e.g. in JIRA? 

Yes, it would be particularly helpful if you could provide a complete
standalone test case which demonstrates the problem.

If that's not possible, then perhaps you could gather query plan output
and post that; perhaps the Derby optimizer is choosing a particularly poor
query plan.

> Can anyone suggest how I could work around the OOM error?

You can control Derby's memory usage by simply allocating more memory to
your JVM when you run Derby, typically by specifying -Xmx. Try something
like -Xmx1024m and see if that avoids the out-of-memory problem.

Of course, you don't want to specify a number larger than the actual
amount of physical memory on your computer, so if your computer only has,
e.g., 512m of physical memory, use something like -Xmx384m

You can find some pointers to suggestions about studying Derby performance
issues here: http://wiki.apache.org/db-derby/PerformanceDiagnosisTips

thanks,

bryan


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