drop table if exists t1;
# Establish connection con1 (user=root)
# Switch to connection con1
CREATE TABLE t1 (a INT primary key, b INT)ENGINE=xengine;
insert into t1 values(1,1);
insert into t1 values(2,2);
insert into t1 values(3,3);
insert into t1 values(4,4);
insert into t1 values(5,5);
SET DEBUG_SYNC= 'xengine.inplace_create_sk_scan_base_begin SIGNAL start_dml_insert WAIT_FOR start_dml_insert_finish';
alter table t1 add  index t1_c22 (b) ,ALGORITHM  = INPLACE, LOCK=DEFAULT;
SET DEBUG_SYNC= 'now WAIT_FOR start_dml_insert';
insert into t1 values(6,6);
SET DEBUG_SYNC= 'now SIGNAL start_dml_insert_finish';
# Switch to connection con1
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) NOT NULL,
  `b` int(11) DEFAULT NULL,
  PRIMARY KEY (`a`),
  KEY `t1_c22` (`b`)
) ENGINE=XENGINE DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci
SELECT * FROM t1 USE INDEX (t1_c22) where b = 1;
a	b
1	1
SELECT * FROM t1 USE INDEX (t1_c22) where b = 2;
a	b
2	2
SELECT * FROM t1 USE INDEX (t1_c22) where b = 3;
a	b
3	3
SELECT * FROM t1 USE INDEX (t1_c22) where b = 4;
a	b
4	4
SELECT * FROM t1 USE INDEX (t1_c22) where b = 5;
a	b
5	5
SELECT * FROM t1 USE INDEX (t1_c22) where b = 6;
a	b
6	6
drop table t1;