怎么进行MySQL 5.5 MyISAM表锁测试

这篇文章给大家介绍怎么进行MySQL 5.5 MyISAM表锁测试，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。

对于MyISAM表，加的锁是表级锁；写操作会阻塞读操作，读操作会阻塞写操作，写操作会阻塞写操作；读操作不会阻塞读操作。

测试一，会话①的读操作阻塞会话②的写操作
会话①
mysql> create table t2(id tinyint(3) unsigned not null auto_increment,
    ->  name varchar(10) not null,
    ->  primary key(id))
    ->  engine=myisam auto_increment=8 default charset=gbk;
Query OK, 0 rows affected (0.03 sec)
mysql> insert into t2(name) values('Neo');
Query OK, 1 row affected (0.03 sec)
mysql> insert into t2(name) values('Trinity');
Query OK, 1 row affected (0.00 sec)

mysql> select * from t2;
+----+---------+
| id | name    |
+----+---------+
|  8 | Neo     |
|  9 | Trinity |
+----+---------+
2 rows in set (0.00 sec)

mysql> desc t2;
+-------+---------------------+------+-----+---------+----------------+
| Field | Type                | Null | Key | Default | Extra          |
+-------+---------------------+------+-----+---------+----------------+
| id    | tinyint(3) unsigned | NO   | PRI | NULL    | auto_increment |
| name  | varchar(10)         | NO   |     | NULL    |                |
+-------+---------------------+------+-----+---------+----------------+
2 rows in set (0.09 sec)

为表增加读锁
mysql> lock table t2 read;
Query OK, 0 rows affected (0.00 sec)

会话②
mysql> select * from t2;
+----+---------+
| id | name    |
+----+---------+
|  8 | Neo     |
|  9 | Trinity |
+----+---------+
2 rows in set (0.00 sec)

会话会处于等待状态
mysql> update t2 set name='James' where id=5;

会话①
mysql> show processlist;
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+---------------------------------------+
| Id | User            | Host      | db   | Command | Time   | State                                                                       | Info                                  |
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+---------------------------------------+
|  1 | system user     |           | NULL | Connect | 748155 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL                                  |
|  2 | system user     |           | NULL | Connect | 748156 | Connecting to master                                                        | NULL                                  |
| 13 | event_scheduler | localhost | NULL | Daemon  | 600105 | Waiting on empty queue                                                      | NULL                                  |
| 74 | neo             | localhost | fire | Query   |      0 | NULL                                                                        | show processlist                      |
| 75 | neo             | localhost | fire | Query   |     83 | Waiting for table level lock                                                | update t2 set name='James' where id=5 |
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+---------------------------------------+
5 rows in set (0.00 sec)

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

会话②
mysql> update t2 set name='James' where id=5;
Query OK, 0 rows affected (1 min 48.96 sec)
Rows matched: 0  Changed: 0  Warnings: 0

测试二，会话①的写操作阻塞会话②的读操作

会话①
mysql> lock table t2 write;
Query OK, 0 rows affected (0.00 sec)

mysql> insert into t2(name) values('Jack');
Query OK, 1 row affected (0.01 sec)

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

mysql> show processlist;
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+------------------+
| Id | User            | Host      | db   | Command | Time   | State                                                                       | Info             |
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+------------------+
|  1 | system user     |           | NULL | Connect | 748422 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL             |
|  2 | system user     |           | NULL | Connect | 748423 | Connecting to master                                                        | NULL             |
| 13 | event_scheduler | localhost | NULL | Daemon  | 600372 | Waiting on empty queue                                                      | NULL             |
| 74 | neo             | localhost | fire | Query   |      0 | NULL                                                                        | show processlist |
| 75 | neo             | localhost | fire | Query   |      2 | Waiting for table metadata lock                                             | select * from t2 |
+----+-----------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+------------------+
5 rows in set (0.00 sec)

会话②
查询会阻塞
mysql> select * from t2;

会话①
mysql> unlock tables;
Query OK, 0 rows affected (0.00 sec)

会话②
mysql> select * from t2;
+----+---------+
| id | name    |
+----+---------+
|  8 | Neo     |
|  9 | Trinity |
| 10 | Jack    |
+----+---------+
3 rows in set (47.89 sec)

当同一个会话中，锁定一张表后，查询另外一张表会报错
mysql> lock table test read;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test where id=80;
+------+------+
| id   | name |
+------+------+
|   80 | Lily |
+------+------+
1 row in set (0.00 sec)

mysql> select * from t70;
ERROR 1100 (HY000): Table 't70' was not locked with LOCK TABLES

使用表的别名会报错
mysql> lock table test read;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test t where id=80;
ERROR 1100 (HY000): Table 't' was not locked with LOCK TABLES

需要对别名进行锁定

mysql> lock table test t read;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test t where id=80;
+------+------+
| id   | name |
+------+------+
|   80 | Kame |
+------+------+
1 row in set (0.00 sec)

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