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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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