Mysqldiff error: when the associated query primary key index is established on multiple columns, the diff result is wrong

[lizhiyou88]

table structure in server1:
CREATE TABLE t1 (
a int NOT NULL,
b char(10) NOT NULL,
c varchar(100) DEFAULT '',
PRIMARY KEY (a,b),
KEY idx_a_b (a,b)
)

table structure in server2:
CREATE TABLE t1 (
a int(11) NOT NULL AUTO_INCREMENT,
b char(10) DEFAULT NULL COMMENT '保证金',
c varchar(100) NOT NULL DEFAULT '',
d datetime DEFAULT NULL,
e datetime DEFAULT NULL,
PRIMARY KEY (a),
KEY idx_b_c (b,c)
)

--changes-for=server1 result ：
ALTER TABLE test.t1
DROP PRIMARY KEY,
DROP PRIMARY KEY,
DROP INDEX idx_a_b,
ADD PRIMARY KEY(a),
ADD INDEX idx_b_c (b,c),
CHANGE COLUMN a a int(11) NOT NULL AUTO_INCREMENT,
ADD COLUMN e datetime NULL,
ADD COLUMN d datetime NULL AFTER c,
CHANGE COLUMN c c varchar(100) NOT NULL DEFAULT '',
CHANGE COLUMN b b char(10) NULL COMMENT '保证金',
AUTO_INCREMENT=3, COLLATE=utf8_general_ci;

If it is a federated primary key, "drop primary key" will generate multiple primary keys