SHOW PROCESSLIST Syntax

SHOW PROCESSLIST shows you which threads are running. You can also get this information from the INFORMATION_SCHEMA PROCESSLIST table or the mysqladmin processlist command. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using). If you do not use the FULL keyword, only the first 100 characters of each statement are shown in the Info field.

Process information is also available from the performance_schema.threads table. However, access to threads does not require a mutex and has minimal impact on server performance. INFORMATION_SCHEMA.PROCESSLIST and SHOW PROCESSLIST have negative performance consequences because they require a mutex. threads also shows information about background threads, which INFORMATION-SCHEMA.PROCESSLIST and SHOW PROCESSLIST do not. This means that threads can be used to monitor activity the other thread information sources cannot.

The SHOW PROCESSLIST statement is very useful if you get the "too many connections" error message and want to find out what is going on. MariaDB reserves one extra connection to be used by accounts that have the SUPER privilege, to ensure that administrators should always be able to connect and check the system (assuming that you are not giving this privilege to all your users).

Threads can be killed with the KILL statement. See , "KILL Syntax".

Here is an example of SHOW PROCESSLIST output:

mysql> SHOW FULL PROCESSLIST\G
*************************** 1. row ***************************
Id: 1
User: system user Host:
db: NULL Command: Connect Time: 1030455
State: Waiting for master to send event Info: NULL
*************************** 2. row ***************************
Id: 2
User: system user Host:
db: NULL Command: Connect Time: 1004
State: Has read all relay log; waiting for the slave
 I/O thread to update it Info: NULL
*************************** 3. row ***************************
Id: 3112
User: replikator Host: artemis:2204
db: NULL Command: Binlog Dump Time: 2144
State: Has sent all binlog to slave; waiting for binlog to be updated Info: NULL
*************************** 4. row ***************************
Id: 3113
User: replikator Host: iconnect2:45781
db: NULL Command: Binlog Dump Time: 2086
State: Has sent all binlog to slave; waiting for binlog to be updated Info: NULL
*************************** 5. row ***************************
Id: 3123
User: stefan Host: localhost db: apollon Command: Query Time: 0
State: NULL Info: SHOW FULL PROCESSLIST
5 rows in set (0.00 sec)

The columns produced by SHOW PROCESSLIST have the following meanings:

• Id

  The connection identifier.

• User

  The MariaDB user who issued the statement. If this is system user, it refers to a nonclient thread spawned by the server to handle tasks internally. This could be the I/O or SQL thread used on replication slaves or a delayed-row handler. unauthenticated user refers to a thread that has become associated with a client connection but for which authentication of the client user has not yet been done. event_scheduler refers to the thread that monitors scheduled events. For system user, there is no host specified in the Host column.

• Host

  The host name of the client issuing the statement (except for system user where there is no host). SHOW PROCESSLIST reports the host name for TCP/IP connections in host_name:client_port format to make it easier to determine which client is doing what.

• db

  The default database, if one is selected, otherwise NULL.

• Command

  The type of command the thread is executing. For descriptions for thread commands, see , "Examining Thread Information". The value of this column corresponds to the COM_xxx commands of the client/server protocol and Com_xxx status variables. See , "Server Status Variables"

• Time

  The time in seconds that the thread has been in its current state.

• State

  An action, event, or state that indicates what the thread is doing. Descriptions for State values can be found at , "Examining Thread Information".

  Most states correspond to very quick operations. If a thread stays in a given state for many seconds, there might be a problem that needs to be investigated.

  For the SHOW PROCESSLIST statement, the value of State is NULL.

• Info

  The statement the thread is executing, or NULL if it is not executing any statement. The statement might be the one sent to the server, or an innermost statement if the statement executes other statements. For example, if a CALL statement executes a stored procedure that is executing a SELECT statement, the Info value shows the SELECT statement.

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