KILL [HARD | SOFT] [CONNECTION | QUERY [ID] ] [thread_id | USER user_name | query_id]
HARD | SOFT and
USER username were introduced in MariaDB 5.3.2
KILL QUERY ID query_id, which permits killing a query by query id rather than thread id, was introduced in MariaDB 10.0.5.
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 thread_id statement.
KILL allows the optional
KILL CONNECTIONis the same as
KILLwith no modifier: It terminates the connection associated with the given thread or query id.
KILL QUERYterminates the statement that the connection thread_id is currently executing, but leaves the connection itself intact.
KILL QUERY ID(introduced in MariaDB 10.0.5) terminates the query by query_id, leaving the connection intact.
If a connection is terminated that has an active transaction, the transaction will be rolled back. If only a query is killed, the current transaction will stay active.
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
Killing queries that repair or create indexes on MyISAM and Aria tables may result in corrupted tables.
HARD option (default) kills a command as soon as possible. If you use
SOFT, then critical operations that may leave a table in an
inconsistent state will not be interrupted. Such operations include
INDEX creation for MyISAM and Aria tables (REPAIR TABLE, OPTIMIZE TABLE).
KILL ... USER username will kill all connections/queries for a
USER can be specified one of the following ways:
If you specify a thread id and that thread does not exist, you get the following error:
ERROR 1094 (HY000): Unknown thread id: <thread_id>
If you specify a query id that doesn't exist, you get the following error:
ERROR 1957 (HY000): Unknown query id: <query_id>
However, if you specify a user name, no error is issued for non-connected (or even non-existing) users. To check if the connection/query has been killed, you can use the ROW_COUNT() function.
A client whose connection is killed receives the following error:
ERROR 1317 (70100): Query execution was interrupted
Note: 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.
Note: You can also use
mysqladmin kill thread_id [,thread_id...]
to kill connections. To get a list of running queries,
mysqladmin processlist. See mysqladmin.
Percona Toolkit contains a program, pt-kill that can be used to automatically kill connections that match certain criteria. For example, it can be used to terminate idle connections, or connections that have been busy for more than 60 seconds.