I'm having a problem where a complex SELECT query begins eating up lots of CPU and never returns. In "show processlist", it reports "Copying to tmp table". Other queries seem to get locked waiting for this query, as well. This is on version 3.23.36 of mySQL, and I'm considering upgrading to the latest 3.23.57, to see if that improves the performance. I can't find any matching references in the Changes web pages that indicate this, though. Can anyone verify this? Alternately, I'm trying to find ways to possibly improve the step of "copying to tmp table". According to my "show variables" output, the "tmpdir" is /tmp, and /tmp has plenty of room (85 megs or so). But while the query is running, I don't even see a corresponding file there. The CPU is spiking with top reporting mysql as eating 85% CPU. So I then assume that the 'problem' is happening before the file is created? Does that sound right? If someone has a better reference for tracking down the source of a problem like this, other than http://www.mysql.com/doc/en/MySQL_Optimisation.html, I'd be very appreciative. thanks, Kevin Fries
