From: Zardosht Kasheff
Date: September 25 2009 2:41pm
Subject: is MySQL query execution single threaded?
List-Archive: http://lists.mysql.com/internals/37328
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Hello all,

I want to maintain some statistics while a statement is executing
(number of rows inserted, updated, deleted, or read). If query
execution is single threaded (e.g. two handlers will not be reading
rows from different indexes in parallel for an index merge), then
maintaining these statistics becomes easy. I do not have to worry
about concurrency issues.

With that said, is query execution single-threaded? Or are threads
spawned for parallel execution?

Thanks
-Zardosht