create
    definer = `mysql.sys`@localhost function sys.ps_is_consumer_enabled(in_consumer varchar(64)) returns enum ('YES', 'NO')
    comment '
Description
-----------

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

An exception with errno 3047 is thrown if an unknown consumer name is passed to the function.
A consumer name of NULL returns NULL.

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)
'
    deterministic
    sql security invoker
    reads sql data
BEGIN
    DECLARE v_is_enabled ENUM('YES', 'NO') DEFAULT NULL;
    DECLARE v_error_msg VARCHAR(128);
    -- Return NULL for a NULL argument.
    IF (in_consumer IS NULL) THEN
        RETURN NULL;
    END IF;
    SET v_is_enabled = (
        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
        );
    IF (v_is_enabled IS NOT NULL) THEN
        RETURN v_is_enabled;
    ELSE
        -- A value of NULL here means it is an unknown consumer name that was passed as an argument.
        -- Only an input value of NULL is allowed to return a NULL result value, to throw a signal instead.
        SET v_error_msg = CONCAT('Invalid argument error: ', in_consumer, ' in function sys.ps_is_consumer_enabled.');
        SIGNAL SQLSTATE 'HY000'
           SET MESSAGE_TEXT = v_error_msg,
               MYSQL_ERRNO  = 3047;
    END IF;
END;