From: Zardosht Kasheff Date: February 12 2013 1:54pm Subject: debugging how query plans are made List-Archive: http://lists.mysql.com/internals/38723 Message-Id: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Hello all, In MySQL and/or MariaDB, are there any hooks or methods one can use to learn why a query plan is chosen over alternatives? We sometimes notice that a different query plan is chosen for us than InnoDB (which may be fine, given we are a different storage engine), and we would like to better understand why. Is there any debug parameter that gets MySQL to output decisions made in the optimizer? Thanks -Zardosht