Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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SHOW [FULL] PROCESSLIST
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 MySQL
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. MySQL 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 Section 13.7.6.4, "KILL Syntax".
Here is an example of SHOW
PROCESSLIST output:
mysql> SHOW FULL PROCESSLIST\G*************************** 1. row ***************************Id: 1User: system userHost:db: NULLCommand: ConnectTime: 1030455State: Waiting for master to send eventInfo: NULL*************************** 2. row ***************************Id: 2User: system userHost:db: NULLCommand: ConnectTime: 1004State: Has read all relay log; waiting for the slave I/O thread to update itInfo: NULL*************************** 3. row ***************************Id: 3112User: replikatorHost: artemis:2204db: NULLCommand: Binlog DumpTime: 2144State: Has sent all binlog to slave; waiting for binlog to be updatedInfo: NULL*************************** 4. row ***************************Id: 3113User: replikatorHost: iconnect2:45781db: NULLCommand: Binlog DumpTime: 2086State: Has sent all binlog to slave; waiting for binlog to be updatedInfo: NULL*************************** 5. row ***************************Id: 3123User: stefanHost: localhostdb: apollonCommand: QueryTime: 0State: NULLInfo: SHOW FULL PROCESSLIST5 rows in set (0.00 sec)
The columns produced by SHOW
PROCESSLIST have the following meanings:
Id
The connection identifier.
User
The MySQL 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
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 Section 8.12.5, "Examining Thread Information".
The value of this column corresponds to the COM_
commands of the client/server protocol and xxxCom_
status variables. See Section 5.1.6, "Server Status
Variables"xxx
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 Section
8.12.5, "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.