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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject Re: interested in working on DERBY-713
Date Mon, 19 Jun 2006 18:30:08 GMT
Hi Brent,

Sounds like you're off to a good start. From the initial bug report, it 
looks like there's a good idea about which heuristic is being 
mis-applied here. Once you've studied the optimizer papers, I recommend 
that you post some high-level candidate solutions. Try to avoid 
optimizer jargon and concentrate on simple descriptions:

o What query plan would you rather see?
o What heuristic would the optimizer apply that would lead it to your 
preferred plan?
o How would the optimizer decide to apply the new heuristic rather than 
the old one?

I think you'll get some good feedback if your post contains the phrase 
"Attention, optimizer experts." I think that the optimizer enthusiasts 
on the list will give you good feedback:

o Maybe they can think of a better query plan or heuristic.
o Maybe they can see some awkward corner cases in your  heuristic.
o They can advise you on whether your heuristic will short-circuit other 
optimizer choices.
o They can advise you on whether your heuristic will cause an explosion 
in the time that the optimizer takes.

Thanks for wanting to scratch this itch!


Brent Verner wrote:

>	I've recently found need for an embedded java db and only Derby seems
>even close to handling the task, however the broken query planning for IN
>clauses makes it unusable :-(.  I've decided to eschew an embedded db
>in favor of PG for now, but I'd really like to be able to use Derby in the
>near(ish) future for deployment.
>	I'd like to try to fix the query planning around the IN clause.  I'm
>reviewing the internals papers right now, but I'd appreciate any input
>that might point me in the right direction :-).
>  Brent

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