ps_setup_enable_thread()

• 启用指定的线程检测功能，通过修改performance_schema.threads表，调用时传入值作为processlist_id字段值，修改instrumented字段为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）

• 参数：

  • in_connection_id BIGINT：连接ID(进程ID)，为performance_schema.theads表的PROCESSLIST_ID列或SHOW PROCESSLIST输出的id列值

• 定义语句

DROP PROCEDURE IF EXISTS ps_setup_enable_thread;

DELIMITER $$

CREATE DEFINER='root'@'localhost' PROCEDURE ps_setup_enable_thread (
        IN in_connection_id BIGINT
    )
    COMMENT '
            Description
            -----------

            Enable the given connection/thread in Performance Schema.

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

            in_connection_id (BIGINT):
              The connection ID (PROCESSLIST_ID from performance_schema.threads
              or the ID shown within SHOW PROCESSLIST)

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

            mysql> CALL sys.ps_setup_enable_thread(3);
            +------------------+
            | summary          |
            +------------------+
            | Enabled 1 thread |
            +------------------+
            1 row in set (0.01 sec)

            To enable the current connection:

            mysql> CALL sys.ps_setup_enable_thread(CONNECTION_ID());
            +------------------+
            | summary          |
            +------------------+
            | Enabled 1 thread |
            +------------------+
            1 row in set (0.00 sec)
            '
    SQL SECURITY INVOKER
    NOT DETERMINISTIC
    MODIFIES SQL DATA
BEGIN
    UPDATE performance_schema.threads
      SET instrumented = 'YES'
    WHERE processlist_id = in_connection_id;

    SELECT CONCAT('Enabled ', @rows := ROW_COUNT(), ' 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-thread.html

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