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Re: Parallel scans
Posted by: Rick James
Date: May 20, 2009 10:39PM

You have pretty much described the "index merge", new with 5.0:
http://dev.mysql.com/doc/refman/5.0/en/index-merge-optimization.html

Your particular example had two things conspiring from picking t2 first (which would have been much more efficient): LEFT JOIN and 'f' being NULLable.

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Parallel scans
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Steve Fink
May 19, 2009 04:15PM
Re: Parallel scans
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Rick James
May 20, 2009 10:39PM


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