MySQL 9.0 Release Notes
A thread can have any of the following
Command values:
This is a thread on a replication source for sending binary log contents to a replica.
The thread is executing a change user operation.
The thread is closing a prepared statement.
Used by replication receiver threads connected to the source, and by replication worker threads.
A replica is connecting to its source.
The thread is executing a create database operation.
This thread is internal to the server, not a thread that services a client connection.
The thread is generating debugging information.
The thread is a delayed insert handler.
The thread is executing a drop database operation.
The thread is executing a prepared statement.
The thread is fetching the results from executing a prepared statement.
The thread is retrieving information for table columns.
The thread is selecting a default database.
The thread is killing another thread.
The thread is retrieving long data in the result of executing a prepared statement.
The thread is handling a server ping request.
The thread is preparing a prepared statement.
The thread is producing information about server threads.
Employed for user clients while executing queries by single-threaded replication applier threads, as well as by the replication coordinator thread.
The thread is terminating.
The thread is flushing table, logs, or caches, or resetting status variable or replication server information.
The thread is registering a replica server.
The thread is resetting a prepared statement.
The thread is setting or resetting a client statement execution option.
The thread is shutting down the server.
The thread is waiting for the client to send a new statement to it.
The thread is producing server status information.
Unused.