CREATE TABLE t1(c1 INT NOT NULL, c2 INT, PRIMARY KEY(c1))ENGINE=INNODB;
INSERT INTO t1 VALUES(1, 1);
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
affected rows: 0
ALTER TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2;
connect  con1,localhost,root;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
affected rows: 0
INSERT INTO t1 VALUES(2, NULL);
affected rows: 1
UPDATE t1 SET c1 = 3 WHERE c2 = 1;
affected rows: 1
info: Rows matched: 1  Changed: 1  Warnings: 0
SET DEBUG_SYNC= 'now SIGNAL flushed';
affected rows: 0
connection default;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 1
Warnings:
Warning	1265	Data truncated for column 'c2' at row 3
SELECT * FROM t1;
c1	c2
2	0
3	1
DROP TABLE t1;
CREATE TABLE t1(c1 INT NOT NULL, c2 INT, PRIMARY KEY(c1))ENGINE=INNODB;
INSERT INTO t1 VALUES(1, 1);
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
affected rows: 0
ALTER TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2;
connection con1;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
affected rows: 0
INSERT INTO t1 VALUES(2, 3);
affected rows: 1
UPDATE t1 SET c1 = 3 WHERE c2 = 1;
affected rows: 1
info: Rows matched: 1  Changed: 1  Warnings: 0
SET DEBUG_SYNC= 'now SIGNAL flushed';
affected rows: 0
connection default;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
SELECT * FROM t1;
c1	c2
2	3
3	1
DROP TABLE t1;
CREATE TABLE t1(c1 INT NOT NULL, c2 INT, c3 INT, PRIMARY KEY(c1))ENGINE=INNODB;
INSERT INTO t1 VALUES(1, 2, 3);
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
affected rows: 0
ALTER IGNORE TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2;
connection con1;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
affected rows: 0
UPDATE t1 SET c2= 2 WHERE c1 = 1;
affected rows: 0
info: Rows matched: 1  Changed: 0  Warnings: 0
INSERT INTO t1 VALUES (2, NULL, 4);
affected rows: 1
SET DEBUG_SYNC= 'now SIGNAL flushed';
affected rows: 0
connection default;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 1
Warnings:
Warning	1265	Data truncated for column 'c2' at row 3
SELECT * FROM t1;
c1	c2	c3
1	2	3
2	0	4
DROP TABLE t1;
disconnect con1;
SET DEBUG_SYNC='RESET';