[CMT8.4.1.1209]After migration, the index order become to error.

1There is table
CREATE TABLE `a` (
`a` int(11) NOT NULL DEFAULT '0',
`b` int(11) DEFAULT NULL,
`c` int(11) DEFAULT NULL,
`d` int(11) DEFAULT '0',
PRIMARY KEY (`a`),
KEY `a_b_id` (`b`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

– ----------------------------
– Records
– ----------------------------
INSERT INTO `a` VALUES ('0', '1', null, '0');
INSERT INTO `a` VALUES ('1', '1', null, '0');
INSERT INTO `a` VALUES ('2', '2', null, '0');
INSERT INTO `a` VALUES ('3', '3', null, '0');
2 Do migration from online to online.

Actual result:
The index become to desc.