28.3.23 The INFORMATION_SCHEMA PROCESSLIST Table (original) (raw)

28.3.23 The INFORMATION_SCHEMA PROCESSLIST Table

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, see Sources of Process Information.

The PROCESSLIST table has these columns:

• ID
  The connection identifier. This is the same value displayed in the Id column of theSHOW PROCESSLIST statement, displayed in the PROCESSLIST_ID column of the Performance Schema threads table, and returned by theCONNECTION_ID() function within the thread.
• USER
  The MySQL user who issued the statement. A value ofsystem 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 (seeSection 27.4, “Using the Event Scheduler”).
  Note
  A USER value of system user is distinct from theSYSTEM_USER privilege. The former designates internal threads. The latter distinguishes the system user and regular user account categories (seeSection 8.2.11, “Account Categories”).
• HOST
  The host name of the client issuing the statement (except forsystem user, for which there is no host). The host name for TCP/IP connections is reported in_`hostname`_:_`clientport`_ format to make it easier to determine which client is doing what.
• DB
  The default database for the thread, orNULL 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 10.14, “Examining Server Thread (Process) Information”. The value of this column corresponds to theCOM_ _`xxx`_ commands of the client/server protocol andCom_ _`xxx`_ status variables. See Section 7.1.10, “Server Status Variables”.
• 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 19.2.3, “Replication Threads”.
• STATE
  An action, event, or state that indicates what the thread is doing. For descriptions of STATE values, see Section 10.14, “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.
• INFO
  The statement the thread is executing, orNULL 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 aSELECT statement, theINFO value shows theSELECT statement.

Notes

• PROCESSLIST is a nonstandardINFORMATION_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 the PROCESS 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 thePROCESSLIST 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

You can obtain information about use of this table by checking the values of the server status variablesDeprecated_use_i_s_processlist_count andDeprecated_use_i_s_processlist_last_timestamp.Deprecated_use_i_s_processlist_count shows the number of times the PROCESSLIST table has been accessed since the last server restart;Deprecated_use_i_s_processlist_last_timestamp provides the last time the table was accessed, as a Unix timestamp.