KILL [CONNECTION | QUERY] thread_id
Each connection to mysqld runs in a separate
thread. You can see which threads are running with the
SHOW PROCESSLIST statement and
kill a thread with the KILL
statement.
thread_id
KILL permits an optional
CONNECTION or QUERY
modifier:
KILL CONNECTIONis the same asKILLwith no modifier: It terminates the connection associated with the giventhread_id.KILL QUERYterminates the statement that the connection is currently executing, but leaves the connection itself intact.
If you have the PROCESS
privilege, you can see all threads. If you have the
SUPER privilege, you can kill all
threads and statements. Otherwise, you can see and kill only
your own threads and statements.
You can also use the mysqladmin processlist and mysqladmin kill commands to examine and kill threads.
You 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 any connection threads of its own.
When you use KILL, a
thread-specific kill flag is set for the thread. In most cases,
it might take some time for the thread to die because the kill
flag is checked only at specific intervals:
In
SELECT,ORDER BYandGROUP BYloops, the flag is checked after reading a block of rows. If the kill flag is set, the statement is aborted.During
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 statement is aborted and the temporary table is deleted.During
UPDATEorDELETEoperations, 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 are not rolled back.GET_LOCK()aborts and returnsNULL.An
INSERT DELAYEDthread quickly flushes (inserts) all rows it has in memory and then terminates.If the thread is in the table lock handler (state:
Locked), the table lock is quickly aborted.If the thread is waiting for free disk space in a write call, the write is aborted with a “disk full” error message.
- Warning
Killing a
REPAIR TABLEorOPTIMIZE TABLEoperation on aMyISAMtable results in a table that is corrupted and unusable. Any reads or writes to such a table fail until you optimize or repair it again (without interruption).