25.40 INFORMATION_SCHEMA Thread Pool Tables

Note

As of MySQL 8.0.14, the thread pool INFORMATION_SCHEMA tables are also available as Performance Schema tables. (See Section 26.12.15, “Performance Schema Thread Pool Tables”.) The INFORMATION_SCHEMA tables are deprecated and will be removed in a future MySQL version. Applications should transition away from the old tables to the new tables. For example, if an application uses this query:

SELECT * FROM INFORMATION_SCHEMA.TP_THREAD_STATE;

The application should use this query instead:

SELECT * FROM performance_schema.tp_thread_state;

The following sections describe the INFORMATION_SCHEMA tables associated with the thread pool plugin (see Section 5.6.3, “MySQL Enterprise Thread Pool”). They provide information about thread pool operation:

TP_THREAD_GROUP_STATE: Information about thread pool thread group states
TP_THREAD_GROUP_STATS: Thread group statistics
TP_THREAD_STATE: Information about thread pool thread states

Rows in these tables represent snapshots in time. In the case of TP_THREAD_STATE, all rows for a thread group comprise a snapshot in time. Thus, the MySQL server holds the mutex of the thread group while producing the snapshot. But it does not hold mutexes on all thread groups at the same time, to prevent a statement against TP_THREAD_STATE from blocking the entire MySQL server.

The INFORMATION_SCHEMA thread pool tables are implemented by individual plugins and the decision whether to load one can be made independently of the others (see Section 5.6.3.2, “Thread Pool Installation”). However, the content of all the tables depends on the thread pool plugin being enabled. If a table plugin is enabled but the thread pool plugin is not, the table becomes visible and can be accessed but will be empty.

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Document created the 26/06/2006, last modified the 26/10/2018
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References

Manuel MySQL : https://dev.mysql.com/

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