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Date: Wed, 15 Nov 2006 10:06:07 -0800
From: Bryan Pendleton <bpendleton@amberpoint.com>
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To: derby-dev@db.apache.org
Subject: Optimizer Timeout question
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I've been working my way through Army's awesome Wiki pages
and learning a lot about the Optimizer. I'm doing this in
the context of a problematic query of mine.

I've got a question about how Optimizer Timeout works. See
http://wiki.apache.org/db-derby/LanguageOptimize to set the
context for this question. In particular, I'm interested in
the interaction between the following code loop in
SelectNode.optimize and the optimizer timeout mechanism:

* Optimize this SelectNode */
while (optimizer.getNextPermutation())
{
     while (optimizer.getNextDecoratedPermutation())
     {
         optimizer.costPermutation();
     }
}

So here's the question: as I understand it, the Optimizer
Timeout mechanism kicks in during optimizer.getNextPermutation().
But what if the "inner" while loop has a very large number
of decorated permutations to cost for this particular pass through
the outer loop?

Shouldn't we be checking for timeout in the inner loop as well?

thanks,

bryan