Cannot assign hash distribution with different distribution cols. new is: [`a` varchar(*) NULL ] default is: [`a` varchar(50) ]

DORIS 2.0.5
原来DDL:

CREATE TABLE ads_etest(
	a VARCHAR(50) ,                                    
	serial INT  ,
	piece_x SMALLINT ,
	piece_y SMALLINT ,
	suppiler_code VARCHAR(20) ,
	panel_no  VARCHAR(20)  ,
	set_no  VARCHAR(20),
	apn VARCHAR(30) 
	dt DATEV2 COMMENT ""
)DUPLICATE KEY(`a`,`serial`,`piece_x`,`piece_y`)
PARTITION BY RANGE(`dt`)()
DISTRIBUTED BY HASH(`a`) BUCKETS 8
PROPERTIES (
	"replication_num" = "2",
	"compression" = "zstd",
	"dynamic_partition.enable" = "true", 
	"dynamic_partition.time_unit" = "MONTH", 
	"dynamic_partition.time_zone" = "Asia/Shanghai", ,
	"dynamic_partition.buckets" = "8", 
	"dynamic_partition.prefix" = "p", 
	"dynamic_partition.end" = "6" 
);

开始动态建立分区成功，之后修改了a字段的长度，就失败了，报错：

Cannot assign hash distribution with different distribution cols. new is: [`a` varchar(*) NULL ] default is: [`a` varchar(50) ]