RR模式下利用区间锁防止幻读,RC模式没有区间锁会出现幻读

Session 1:
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from SmsTest where phoneNo between 30 and 40 for update;
+----+---------+-------------+--------+
| sn | phoneNo | channelType | status |
+----+---------+-------------+--------+
| 30 |      30 |           2 |      1 |
| 31 |      31 |           2 |      1 |
| 32 |      32 |           2 |      1 |
| 33 |      33 |           2 |      1 |
| 34 |      34 |           2 |      1 |
| 35 |      35 |           2 |      1 |
| 36 |      36 |           2 |      1 |
| 37 |      37 |           2 |      1 |
| 38 |      38 |           2 |      1 |
| 39 |      39 |           2 |      1 |
| 40 |      40 |           2 |      1 |
+----+---------+-------------+--------+
11 rows in set (0.00 sec)

mysql> explain select * from SmsTest where phoneNo between 30 and 40 for update;
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
| id | select_type | table   | type  | possible_keys | key          | key_len | ref  | rows | Extra                 |
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
|  1 | SIMPLE      | SmsTest | range | SmsTest_idx1  | SmsTest_idx1 | 4       | NULL |   11 | Using index condition |
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
1 row in set (0.00 sec)



Session 2:

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(28,1,1);
Query OK, 1 row affected (0.00 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(29,1,1);  --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(30,1,1);  --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(31,1,1); --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(32,1,1); --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(33,1,1); --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(34,1,1);--hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(40,1,1); --hang

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(41,1,1);
Query OK, 1 row affected (0.01 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(42,1,1);
Query OK, 1 row affected (0.04 sec)


在30-40这个区间无法插入,RR需要区间锁来防止幻读



修改事务隔离为transaction-isolation =READ-COMMITTED  

mysql> select @@tx_isolation; 
+----------------+
| @@tx_isolation |
+----------------+
| READ-COMMITTED |
+----------------+
1 row in set (0.00 sec)

mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from SmsTest where phoneNo between 30 and 40 for update;
+----+---------+-------------+--------+
| sn | phoneNo | channelType | status |
+----+---------+-------------+--------+
| 30 |      30 |           2 |      1 |
| 31 |      31 |           2 |      1 |
| 32 |      32 |           2 |      1 |
| 33 |      33 |           2 |      1 |
| 34 |      34 |           2 |      1 |
| 35 |      35 |           2 |      1 |
| 36 |      36 |           2 |      1 |
| 37 |      37 |           2 |      1 |
| 38 |      38 |           2 |      1 |
| 39 |      39 |           2 |      1 |
| 40 |      40 |           2 |      1 |
+----+---------+-------------+--------+
11 rows in set (0.01 sec)

mysql> explain select * from SmsTest where phoneNo between 30 and 40 for update;
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
| id | select_type | table   | type  | possible_keys | key          | key_len | ref  | rows | Extra                 |
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
|  1 | SIMPLE      | SmsTest | range | SmsTest_idx1  | SmsTest_idx1 | 4       | NULL |   11 | Using index condition |
+----+-------------+---------+-------+---------------+--------------+---------+------+------+-----------------------+
1 row in set (0.01 sec)



Session2:



Database changed
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(28,1,1);
Query OK, 1 row affected (0.00 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(29,1,1); 
Query OK, 1 row affected (0.00 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(30,1,1);
Query OK, 1 row affected (0.00 sec)

mysql> commit;
Query OK, 0 rows affected (0.00 sec)

mysql>  insert into zjzc.SmsTest(PhoneNo,channelType,status)  values(31,1,1);
Query OK, 1 row affected (0.00 sec)


Session 1:

mysql> select * from SmsTest where phoneNo between 30 and 40 for update;
+-------+---------+-------------+--------+
| sn    | phoneNo | channelType | status |
+-------+---------+-------------+--------+
|    30 |      30 |           2 |      1 |
| 45292 |      30 |           1 |      1 |
|    31 |      31 |           2 |      1 |
|    32 |      32 |           2 |      1 |
|    33 |      33 |           2 |      1 |
|    34 |      34 |           2 |      1 |
|    35 |      35 |           2 |      1 |
|    36 |      36 |           2 |      1 |
|    37 |      37 |           2 |      1 |
|    38 |      38 |           2 |      1 |
|    39 |      39 |           2 |      1 |
|    40 |      40 |           2 |      1 |
+-------+---------+-------------+--------+
12 rows in set (0.00 sec)

mysql> select * from SmsTest where phoneNo between 30 and 40 for update;
+-------+---------+-------------+--------+
| sn    | phoneNo | channelType | status |
+-------+---------+-------------+--------+
|    30 |      30 |           2 |      1 |
| 45292 |      30 |           1 |      1 |
|    31 |      31 |           2 |      1 |
| 45293 |      31 |           1 |      1 |
|    32 |      32 |           2 |      1 |
|    33 |      33 |           2 |      1 |
|    34 |      34 |           2 |      1 |
|    35 |      35 |           2 |      1 |
|    36 |      36 |           2 |      1 |
|    37 |      37 |           2 |      1 |
|    38 |      38 |           2 |      1 |
|    39 |      39 |           2 |      1 |
|    40 |      40 |           2 |      1 |
+-------+---------+-------------+--------+
13 rows in set (0.01 sec)


结论 RR模式下 需要区间锁来防止幻读,

     RC模式下,没有区间锁,会出现幻读