怎么進行MySQL 5.5 MyISAM表鎖測試

這篇文章給大家介紹怎么進行MySQL 5.5 MyISAM表鎖測試，內容非常詳細，感興趣的小伙伴們可以參考借鑒，希望對大家能有所幫助。

對于MyISAM表，加的鎖是表級鎖；寫操作會阻塞讀操作，讀操作會阻塞寫操作，寫操作會阻塞寫操作；讀操作不會阻塞讀操作。

測試一，會話①的讀操作阻塞會話②的寫操作
會話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)

為表增加讀鎖
mysql> lock table t2 read;
Query OK, 0 rows affected (0.00 sec)

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

會話會處于等待狀態
mysql> update t2 set name='James' where id=5;

會話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)

會話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

測試二，會話①的寫操作阻塞會話②的讀操作

會話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)

會話②
查詢會阻塞
mysql> select * from t2;

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

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

當同一個會話中，鎖定一張表后，查詢另外一張表會報錯
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

使用表的別名會報錯
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

需要對別名進行鎖定

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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