20.2.4 并发插入

session_1

session_2

获得表film_text的READ LOCAL锁定

mysql> lock table film_text read local;

Query OK, 0 rows affected (0.00 sec)

当前session不能对锁定表进行更新或者插入操作：

mysql> insert into film_text (film_id,title) values(1002,'Test');

ERROR 1099 (HY000): Table 'film_text' was locked with a READ lock and can't be updated

mysql> update film_text set title = 'Test' where film_id = 1001;

ERROR 1099 (HY000): Table 'film_text' was locked with a READ lock and can't be updated

其他session可以进行插入操作，但是更新会等待：

mysql> insert into film_text (film_id,title) values(1002,'Test');

Query OK, 1 row affected (0.00 sec)

mysql> update film_text set title = 'Update Test' where film_id = 1001;

等待

当前session不能访问其他session插入的记录：

mysql> select film_id,title from film_text where film_id = 1002;

Empty set (0.00 sec)

释放锁：

mysql> unlock tables;

Query OK, 0 rows affected (0.00 sec)

等待

当前session解锁后可以获得其他session插入的记录：

mysql> select film_id,title from film_text where film_id = 1002;

+---------+-------+

| film_id | title |

+---------+-------+

| 1002    | Test  |

+---------+-------+

1 row in set (0.00 sec)

Session2获得锁，更新操作完成：

mysql> update film_text set title = 'Update Test' where film_id = 1001;

Query OK, 1 row affected (1 min 17.75 sec)

Rows matched: 1  Changed: 1  Warnings: 0