The MySQL process list indicates the operations currently being performed by the set of threads executing within the server. ThePROCESSLIST
table is one source of process information. For a comparison of this table with other sources, seeSources of Process Information。
ThePROCESSLIST
table has these columns:
ID
The connection identifier. This is the same value displayed in the
Id
column of theSHOW PROCESSLIST
statement, displayed in thePROCESSLIST_ID
column of the Performance Schemathreads
table, and returned by theCONNECTION_ID()
function within the thread.USER
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. Forsystem user
, there is no host specified in theHost
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 (seeSection 25.4, “Using the Event Scheduler”).NoteA
USER
value ofsystem user
is distinct from theSYSTEM_USER
privilege. The former designates internal threads. The latter distinguishes the system user and regular user account categories (seeSection 6.2.11, “Account Categories”).HOST
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
DB
The default database for the thread, or
NULL
if none has been selected.COMMAND
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, seeSection 8.14, “Examining Server Thread (Process) Information”。这一列对应的值COM_
和命令的客户机/服务器协议xxx
Com_
status variables. SeeSection 5.1.10, “Server Status Variables”。xxx
TIME
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. SeeSection 17.2.3, “Replication Threads”。
STATE
An action, event, or state that indicates what the thread is doing. For descriptions of
STATE
values, seeSection 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.
信息
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 aCALL
statement executes a stored procedure that is executing aSELECT
statement, the信息
value shows theSELECT
statement.
Notes
PROCESSLIST
is a nonstandard信息RMATION_SCHEMA
table.Like the output from the
SHOW PROCESSLIST
statement, thePROCESSLIST
table provides information about all threads, even those belonging to other users, if you have thePROCESS
privilege. Otherwise (without thePROCESS
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.If an SQL statement refers to the
PROCESSLIST
table, MySQL populates the entire table once, when statement execution begins, so there is read consistency during the statement. There is no read consistency for a multi-statement transaction.
The following statements are equivalent:
SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST SHOW FULL PROCESSLIST