CREATE TABLE t1(c1 INT NOT NULL, c2 INT, PRIMARY KEY(c1))ENGINE=INNODB;
INSERT INTO t1 VALUES(1, NULL);
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
ALTER TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2, ALGORITHM=INPLACE;
connect  con1,localhost,root;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
INSERT INTO t1 VALUES(2, NULL);
SET DEBUG_SYNC= 'now SIGNAL flushed';
connection default;
ERROR 22004: Invalid use of NULL value
SELECT * FROM t1;
c1	c2
1	NULL
2	NULL
UPDATE t1 SET c2 = 0 WHERE c1 = 2;
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
# Alter ignore can convert the NULL values from
# CONCURRENT DML to constants
ALTER IGNORE TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2, ALGORITHM=INPLACE;
connection con1;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
UPDATE t1 SET c2 = NULL WHERE c1 = 2;
INSERT INTO t1 VALUES (3, NULL);
SET DEBUG_SYNC= 'now SIGNAL flushed';
connection default;
SELECT * FROM t1;
c1	c2
1	2
2	2
3	2
DROP TABLE t1;
CREATE TABLE t1(c1 INT NOT NULL, c2 INT, c3 INT, PRIMARY KEY(c1))ENGINE=INNODB;
INSERT INTO t1 VALUES(1, NULL, NULL);
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
# Alter Successfully converts from null to not null
ALTER TABLE t1 CHANGE c2 c2 INT NOT NULL DEFAULT 2, ALGORITHM=INPLACE;
connection con1;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
UPDATE t1 SET c2= 2 WHERE c1 = 1;
INSERT INTO t1 VALUES (2, 3, 4);
SET DEBUG_SYNC= 'now SIGNAL flushed';
connection default;
SELECT * FROM t1;
c1	c2	c3
1	2	NULL
2	3	4
SET DEBUG_SYNC= 'row_merge_after_scan
SIGNAL opened WAIT_FOR flushed';
# Alter fails because concurrent dml inserts null value
ALTER TABLE t1 CHANGE c3 c3 INT NOT NULL DEFAULT 2, ALGORITHM=INPLACE;
connection con1;
SET DEBUG_SYNC= 'now WAIT_FOR opened';
UPDATE t1 SET c3= 2 WHERE c1 = 2;
INSERT INTO t1 VALUES (4, 3, NULL);
SET DEBUG_SYNC= 'now SIGNAL flushed';
connection default;
ERROR 22004: Invalid use of NULL value
SELECT * FROM t1;
c1	c2	c3
1	2	NULL
2	3	2
4	3	NULL
DROP TABLE t1;
disconnect con1;
SET DEBUG_SYNC='RESET';