Have you ever tried to kill a query, but rather than just go away, it remained among the running ones for an extended period of time? Or perhaps you have noticed some threads makred with killed showing up from time to time and not actually dying. What are these zombies? Why does MySQL sometimes seem to fail to terminate queries quickly? Is there any way to force the kill command to actually work instantaneously? This article sheds some light on it.
Threads and connections
MySQL uses a separate thread for each client connection. A query sent to MySQL is handled by a thread that was previously associated with the …[Read more...]