ps_is_consumer_enabled()

• 检查指定的consumers知否真正生效。根据setup_consumers表中所有consumers的enabled字段设置值，按照consumers生效优先级依次检查指定consumers所依赖的consumers配置项是否启用，如果所依赖的consumers都启用时才会返回该consumers为YES，而不仅仅是返回该指定的consumers在setup_consumers中的enabled字段值设置

  • 如果指定的consumers名称无效，则返回NULL

• 参数：

  • in_consumer VARCHAR（64）：要检查是否启用的consumers名称字符串

• 返回值：一个ENUM('YES','NO') 值

• 定义语句

DROP FUNCTION IF EXISTS ps_is_consumer_enabled;

DELIMITER $$

CREATE DEFINER='root'@'localhost' FUNCTION ps_is_consumer_enabled (
        in_consumer varchar(64)
  )
  RETURNS enum('YES', 'NO')
    COMMENT '

            Determines whether a consumer is enabled (taking the consumer hierarchy into consideration)
            within the Performance Schema.

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

            in_consumer VARCHAR(64): 
              The name of the consumer to check.

            Returns
            -----------

            ENUM(\'YES\', \'NO\')

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

            mysql> SELECT sys.ps_is_consumer_enabled(\'events_stages_history\');
            +-----------------------------------------------------+
            | sys.ps_is_consumer_enabled(\'events_stages_history\') |
            +-----------------------------------------------------+
            | NO                                                  |
            +-----------------------------------------------------+
            1 row in set (0.00 sec)
            '
    SQL SECURITY INVOKER
    DETERMINISTIC
    READS SQL DATA
BEGIN
    RETURN (
        SELECT (CASE
                  WHEN c.NAME = 'global_instrumentation' THEN c.ENABLED
                  WHEN c.NAME = 'thread_instrumentation' THEN IF(cg.ENABLED = 'YES' AND c.ENABLED = 'YES', 'YES', 'NO')
                  WHEN c.NAME LIKE '%\_digest'          THEN IF(cg.ENABLED = 'YES' AND c.ENABLED = 'YES', 'YES', 'NO')
                  WHEN c.NAME LIKE '%\_current'          THEN IF(cg.ENABLED = 'YES' AND ct.ENABLED = 'YES' AND c.ENABLED = 'YES', 'YES', 'NO')
                  ELSE IF(cg.ENABLED = 'YES' AND ct.ENABLED = 'YES' AND c.ENABLED = 'YES'
                          AND ( SELECT cc.ENABLED FROM performance_schema.setup_consumers cc WHERE NAME = CONCAT(SUBSTRING_INDEX(c.NAME, '_', 2), '_current')
                              ) = 'YES', 'YES', 'NO')
                END) AS IsEnabled
          FROM performance_schema.setup_consumers c
              INNER JOIN performance_schema.setup_consumers cg
              INNER JOIN performance_schema.setup_consumers ct
        WHERE cg.NAME      = 'global_instrumentation'
              AND ct.NAME  = 'thread_instrumentation'
              AND c.NAME    = in_consumer
      );
END$$

DELIMITER ;

• 参考链接：https://dev.mysql.com/doc/refman/5.7/en/sys-ps-is-consumer-enabled.html

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