title: Mysql Lock times in slow query log
body: <p>I have an application that has been running fine for quite awhile, but recently a couple of items have started popping up in the slow query log. 
  All the queries are complex and ugly multi join select statements that could use refactoring. I believe all of them have blobs, meaning they get written to disk. The part that gets me curious is why some of them have a lock time associated with them. None of the queries have any specific locking protocols set by the application. As far as I know, by default you can read against locks unless explicitly specified.</p>
  
  <p>so my question: What scenarios would cause a select statement  to have to wait for a lock (and thereby be reported in the slow query log)? Assume both INNODB and MYISAM environments.</p>
  
  <p>Could the disk interaction be listed as some sort of lock time? If yes, is there documentation around that says this?</p>
  
  <p>thanks in advance.</p>