create table t1 (
rowid int,
f1    int,
f2    int,
key i1 (f1, f2),
key i2 (f2)) engine=innodb;
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `rowid` int(11) DEFAULT NULL,
  `f1` int(11) DEFAULT NULL,
  `f2` int(11) DEFAULT NULL,
  KEY `i1` (`f1`,`f2`),
  KEY `i2` (`f2`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
insert into `t1` (rowid, f1, f2) values (1, 1, 10), (2, 1, NULL);
connect  a,localhost,root,,;
connect  b,localhost,root,,;
connection a;
start transaction with consistent snapshot;
connection b;
start transaction;
update t1 set f2 = 4  where f1 = 1 and f2 is null;
(b) Number of rows updated:
select row_count();
row_count()
1
insert into t1 values (3, 1, null);
(b) After update and insert query.
select rowid, f1, f2 from t1;
rowid	f1	f2
1	1	10
2	1	4
3	1	NULL
commit;
connection a;
(a) Before the update statement is executed.
select rowid, f1, f2 from t1;
rowid	f1	f2
1	1	10
2	1	NULL
SET SESSION debug_dbug="+d,bug14007649";
update t1 set f2 = 6 where f1 = 1 and f2 is null;
(a) Number of rows updated:
select row_count();
row_count()
1
(a) After the update statement is executed.
select rowid, f1, f2 from t1;
rowid	f1	f2
1	1	10
2	1	NULL
3	1	6
commit;
"The trx with consistent snapshot ended."
select rowid, f1, f2 from t1;
rowid	f1	f2
1	1	10
2	1	4
3	1	6
connection default;
disconnect a;
disconnect b;
drop table t1;