CREATE TABLE t1 (a INT, b VARCHAR(10)) ENGINE=InnoDB
PARTITION BY RANGE(a)
(PARTITION pa VALUES LESS THAN (3),
PARTITION pb VALUES LESS THAN (5));
INSERT INTO t1 VALUES(2,'two'),(2,'two'),(4,'four');
connect ddl,localhost,root,,test;
SET DEBUG_SYNC = 'inplace_after_index_build SIGNAL go WAIT_FOR done';
ALTER TABLE t1 ADD UNIQUE KEY (a,b(3));
connection default;
SET DEBUG_SYNC = 'now WAIT_FOR go';
BEGIN;
SELECT * FROM t1 FOR UPDATE;
a	b
2	two
2	two
4	four
SET DEBUG_SYNC = 'now SIGNAL done';
connection ddl;
ERROR 23000: Duplicate entry '2-two' for key 'a'
connection default;
DELETE FROM t1;
disconnect ddl;
SET DEBUG_SYNC = 'RESET';
CHECK TABLE t1;
Table	Op	Msg_type	Msg_text
test.t1	check	status	OK
DROP TABLE t1;