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Re: Why does MySQL's performance decrease when queries are executed in parallel?
Posted by: dmitry kotelnikov
Date: July 04, 2012 03:29AM

Hey Rick, thanks a lot for your suggestion. The two queries indeed have quite different execution plans, and SHOW WARNING reveals that one of them uses LEFT JOIN under the hood while the other one uses plain JOIN. The thing I still can not wrap my head around is why (on earth!!) the second query can not be effectively run concurrently (i.e. why the number of queries per second decreases when I use several connections)?

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