ps_setup_enable_background_threads()

• 启用所有后台线程检测功能，通过修改performance_schema.threads表，把所有后台线程的instrumented字段设置为YES实现，返回一个被启用监控功能的线程数量（已经处于启用状态的线程不会计数，因为是使用ROW_COUNT()函数作为返回值，该函数只记录发生变更的行）

  • 该存储过程执行时无需给定任何参数

• 定义语句

DROP PROCEDURE IF EXISTS ps_setup_enable_background_threads;

DELIMITER $$

CREATE DEFINER='root'@'localhost' PROCEDURE ps_setup_enable_background_threads ()
    COMMENT '
            Description
            -----------

            Enable all background thread instrumentation within Performance Schema.

            Parameters
            -----------

            None.

            Example
            -----------

            mysql> CALL sys.ps_setup_enable_background_threads();
            +-------------------------------+
            | summary                      |
            +-------------------------------+
            | Enabled 18 background threads |
            +-------------------------------+
            1 row in set (0.00 sec)
            '
    SQL SECURITY INVOKER
    NOT DETERMINISTIC
    MODIFIES SQL DATA
BEGIN
    UPDATE performance_schema.threads
      SET instrumented = 'YES'
    WHERE type = 'BACKGROUND';

    SELECT CONCAT('Enabled ', @rows := ROW_COUNT(), ' background thread', IF(@rows != 1, 's', '')) AS summary;
END$$

DELIMITER ;

• 参考链接：https://dev.mysql.com/doc/refman/5.7/en/sys-ps-setup-enable-background-threads.html

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