information_schema系统表——PROCESSLIST

进程列表

The PROCESSLIST table provides information about which threads are running.

INFORMATION_SCHEMA Name	SHOW Name	Remarks
ID	Id	MySQL extension
USER	User	MySQL extension
HOST	Host	MySQL extension
DB	db	MySQL extension
COMMAND	Command	MySQL extension
TIME	Time	MySQL extension
STATE	State	MySQL extension
INFO	Info	MySQL extension

For an extensive description of the table columns, see Section 13.7.5.29, “SHOW PROCESSLIST Syntax”.

Notes:

• The PROCESSLIST table is a nonstandard table.

• Like the output from the corresponding SHOW statement, the PROCESSLIST table will only show information about your own threads, unless you have the PROCESSprivilege, in which case you will see information about other threads, too. As an anonymous user, you cannot see any rows at all.

• If an SQL statement refers to INFORMATION_SCHEMA.PROCESSLIST, 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, though.

• 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. threadsalso 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 following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST

SHOW FULL PROCESSLIST