mysql 提交讀 可重複讀

環境

mysql> select version();

+------------+
| version() |
+------------+
| 5.6.31-log |
+------------+
1 row in set (0.00 sec)

mysql> select @@global.tx_isolation,@@tx_isolation;

+-----------------------+----------------+
| @@global.tx_isolation | @@tx_isolation |
+-----------------------+----------------+
| read-committed | read-committed |
+-----------------------+----------------+
1 row in set (0.00 sec)

mysql> show create table t\g;

*****
*****
*****
*****
*****
** 1. row **
*****
*****
*****
*****
*****
table: t
create table: create table `t` (
`id` int(11) not null auto_increment,
`comment` varchar(30) default null,
`time` datetime default null,
primary key (`id`)
) engine=innodb auto_increment=2 default charset=utf8
1 row in set (0.00 sec)

#session 1                                          session 2

mysql> begin; mysql> begin;
query ok, 0 rows affected (0.00 sec) query ok, 0 rows affected (0.00 sec)
mysql> select * from t; 
empty set (0.00 sec) 
mysql> insert into t(comment,time) values ('r1',now());
query ok, 1 row affected (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)
mysql> select * from t;
+----+---------+---------------------+
| id | comment | time |
+----+---------+---------------------+
| 1 | r1 | 2016-09-23 15:56:17 |
+----+---------+---------------------+
1 row in set (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)

mysql>

setglobal tx_isolation=
'repeatable-read';
query ok, 0
rows affected (0.00 sec)

mysql> truncate table t;

query ok, 0 rows affected (0.03 sec)

#session 1                                          session 2

mysql> begin; mysql> begin;
query ok, 0 rows affected (0.00 sec) query ok, 0 rows affected (0.00 sec)
mysql> select * from t; 
empty
set (0.00 sec) 
mysql> insert into t(comment,time) values ('r2',now());
query ok, 1 row affected (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)
mysql> select * from t;
empty
set (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)

mysql> truncate table t;

query ok, 0 rows affected (0.03 sec)

#session 1                                          session 2

mysql> begin; mysql> begin;
query ok, 0 rows affected (0.00 sec) query ok, 0 rows affected (0.00 sec)
mysql> select * from t; 
empty set (0.00 sec) 
mysql> insert into t(comment,time) values ('r3',now());
query ok, 1 row affected (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)
mysql> select * from t;
empty set (0.00 sec)
mysql> update t set comment='c3';
query ok, 1 row affected (0.00 sec)
rows matched: 1 changed: 1 warnings: 0
mysql> select * from t;
+----+---------+---------------------+
| id | comment | time |
+----+---------+---------------------+
| 1 | c3 | 2016-09-23 16:53:28 |
+----+---------+---------------------+
1 row in set (0.00 sec)
mysql> commit;
query ok, 0 rows affected (0.00 sec)

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