mysql error 1071: 创建唯一索引时字段长度限制的问题

CREATE TABLE `xxx` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `sys_code` varchar(255) DEFAULT NULL COMMENT '系统编码',
  `module_name` varchar(1000) DEFAULT NULL COMMENT '模块名',
  `call_num` bigint(20) DEFAULT NULL COMMENT '调用次数',
  `cost_dis` varchar(50) DEFAULT NULL COMMENT '耗时分布',
  `date_time` varchar(50) DEFAULT NULL COMMENT '日期时间',
  PRIMARY KEY (`id`),
  UNIQUE KEY `sys_code` (`sys_code`, `module_name`, `cost_dis`, `date_time`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4
> 1071 - Specified key was too long; max key length is 3072 bytes
> 时间: 0s

mysql> show variables like 'innodb_large_prefix';                                                                                                                                                                                                
+---------------------+-------+
| Variable_name       | Value |
+---------------------+-------+
| innodb_large_prefix | ON    |
+---------------------+-------+
1 row in set (0.00 sec)

mysql> show variables like 'innodb_file_format';  
+--------------------+-----------+
| Variable_name      | Value     |
+--------------------+-----------+
| innodb_file_format | Barracuda |
+--------------------+-----------+
1 row in set (0.00 sec)