MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
SHOW [FULL] PROCESSLIST
The MySQL process list indicates the operations currently being
performed by the set of threads executing within the server. The
SHOW PROCESSLIST
statement is one
source of process information. For a comparison of this
statement with other sources, see
Sources of Process Information.
If you have the PROCESS
privilege, you can see all threads, even those belonging to
other users. Otherwise (without the
PROCESS
privilege), nonanonymous
users have access to information about their own threads but not
threads for other users, and anonymous users have no access to
thread information.
Without the FULL
keyword,
SHOW PROCESSLIST
displays only
the first 100 characters of each statement in the
Info
field.
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 Statement”.
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
SHOW PROCESSLIST
output has these
columns:
The connection identifier. This is the same value displayed
in the ID
column of the
INFORMATION_SCHEMA
PROCESSLIST
table, displayed in
the PROCESSLIST_ID
column of the
Performance Schema threads
table, and returned by the
CONNECTION_ID()
function
within the thread.
The MySQL user who issued the statement. A value of
system user
refers to a nonclient thread
spawned by the server to handle tasks internally, for
example, a delayed-row handler thread or an I/O or SQL
thread used on replica hosts. For system
user
, there is no host specified in the
Host
column. 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 occurred.
event_scheduler
refers to the thread that
monitors scheduled events (see
Section 22.4, “Using the Event Scheduler”).
The host name of the client issuing the statement (except
for system user
, for which there is no
host). The host name for TCP/IP connections is reported in
format to make it easier to determine which client is doing
what.
host_name
:client_port
The default database for the thread, or
NULL
if none has been selected.
The type of command the thread is executing on behalf of the
client, or Sleep
if the session is idle.
For descriptions of thread commands, see
Section 8.14, “Examining Server Thread (Process) Information”. The value of this
column corresponds to the
COM_
commands of the client/server protocol and
xxx
Com_
status
variables. See Section 5.1.9, “Server Status Variables”.
xxx
The time in seconds that the thread has been in its current state. For a replica SQL thread, the value is the number of seconds between the timestamp of the last replicated event and the real time of the replica host. See Section 16.2.3, “Replication Threads”.
An action, event, or state that indicates what the thread is
doing. For descriptions of State
values,
see Section 8.14, “Examining Server Thread (Process) 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.
The statement the thread is executing, or
NULL
if it is executing no 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.