4.5.6 KILL Syntax

KILL thread_id

Each connection to mysqld runs in a separate thread. You can see which threads are running with the SHOW PROCESSLIST command and kill a thread with the KILL thread_id command.

If you have the PROCESS privilege, you can see all threads. If you have the SUPER privilege, you can kill all threads. Otherwise, you can only see and kill your own threads.

You can also use the mysqladmin processlist and mysqladmin kill commands to examine and kill threads.

Note: You currently cannot use KILL with the Embedded MySQL Server library, because the embedded server merely runs inside the threads of the host application, it does not create connection threads of its own.

When you do a KILL, a thread-specific kill flag is set for the thread.

In most cases it may take some time for the thread to die as the kill flag is only checked at specific intervals.

• In SELECT, ORDER BY and GROUP BY loops, the flag is checked after reading a block of rows. If the kill flag is set, the statement is aborted.
• When doing an ALTER TABLE the kill flag is checked before each block of rows are read from the original table. If the kill flag was set the command is aborted and the temporary table is deleted.
• When doing an UPDATE or DELETE, the kill flag is checked after each block read and after each updated or deleted row. If the kill flag is set, the statement is aborted. Note that if you are not using transactions, the changes will not be rolled back!
• GET_LOCK() will abort with NULL.
• An INSERT DELAYED thread will quickly flush all rows it has in memory and die.
• If the thread is in the table lock handler (state: Locked), the table lock will be quickly aborted.
• If the thread is waiting for free disk space in a write call, the write is aborted with an disk full error message.

User Comments

Would be advantageous to have an immediate kill command - currently have a v3.23 db that is locked up (I believe waiting on a thread) the thread cannot be killed so the only hope I have is to kill the whole db :(

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