MySQL RR 模式下 事务隔离问题:Session 1:mysql> select * from test;+------+------+| id   | name |+------+------+| NULL | a    ||    2 | b    ||    3 | c    ||    1 | a01  ||    4 | a    ||    4 | a    ||    5 | c    |+------+------+7 rows in set (0.00 sec)mysql> update test set name='a999' where id=1;Query OK, 1 row affected (0.01 sec)Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from test;+------+------+| id   | name |+------+------+| NULL | a    ||    2 | b    ||    3 | c    ||    1 | a999 ||    4 | a    ||    4 | a    ||    5 | c    |+------+------+7 rows in set (0.00 sec)Session 2:mysql>  select * from test ;+------+------+| id   | name |+------+------+| NULL | a    ||    2 | b    ||    3 | c    ||    1 | a01  ||    4 | a    ||    4 | a    ||    5 | c    |+------+------+7 rows in set (0.00 sec)mysql>  select * from test ;+------+------+| id   | name |+------+------+| NULL | a    ||    2 | b    ||    3 | c    ||    1 | a999 ||    4 | a    ||    4 | a    ||    5 | c    |+------+------+7 rows in set (0.00 sec)此时没有开启事务,RR模式下 更新立即被看到/****************************************************Session 2开启事务:SESSION 1:mysql> update test set name='a0101' where id=1;Query OK, 1 row affected (0.00 sec)Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from test;+------+-------+| id   | name  |+------+-------+| NULL | a     ||    2 | b     ||    3 | c     ||    1 | a0101 ||    4 | a     ||    4 | a     ||    5 | c     |+------+-------+7 rows in set (0.00 sec)此时在查看Session 2:mysql>  select * from test ;+------+------+| id   | name |+------+------+| NULL | a    ||    2 | b    ||    3 | c    ||    1 | a999 ||    4 | a    ||    4 | a    ||    5 | c    |+------+------+7 rows in set (0.00 sec)mysql> commit;Query OK, 0 rows affected (0.00 sec)  ---需要手动提交事务mysql>  select * from test ;+------+-------+| id   | name  |+------+-------+| NULL | a     ||    2 | b     ||    3 | c     ||    1 | a0101 ||    4 | a     ||    4 | a     ||    5 | c     |+------+-------+7 rows in set (0.00 sec)