In MySQL 5.7 and earlier, metadata locks were often a source of confusion. The problem is that it is not obvious who holds the metadata lock. In MySQL 5.7, instrumentation of the metadata locks was added to the Performance Schema, and in MySQL 8.0, it is enabled by default. With the instrumentation enabled, it becomes easy to determine who is blocking the connection trying to obtain the lock. This chapter goes through an example of a situation with metadata locks and examines it. First the symptoms are discussed.
The Symptoms
The symptoms of metadata lock contention ...
