mysql性能优化之default_storage_engine
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1：查看mysql的存储引擎信息
1.1 使用show engines命令。
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.01 sec)
Support列， YES表示当前版本支持这个存储引擎， DEFAULT表示该引擎是默认的引擎。NO表示不支持该存储引擎。如下所示，InnoDB是默认的存储引擎。
1.2 可以查看系统变量default_storage_engine或storage_engine
1：default_storage_engine 表示永久表（permanent tables）的默认存储引擎。
2：default_tmp_storage_engine 表示临时表的默认存储引擎。
storage_engine这个系统变量不推荐使用，它已经被系统变量default_storage_engine替代了
mysql> show variables like '%storage_engine%';
+----------------------------+--------+
| Variable_name | Value |
+----------------------------+--------+
| default_storage_engine | InnoDB |
| default_tmp_storage_engine | InnoDB |
| storage_engine | InnoDB |
+----------------------------+--------+
3 rows in set (0.00 sec)
2：如何修改MySQL的默认存储引擎？
2.1 修改my.cnf，在配置文件里面增加参数default-storage-engine，然后重启数据库服务。
[mysqld]
default-storage-engine=MyISAM
然后检查默认存储引擎，就会看到MyISAM为默认存储引擎了。
2.2 使用命令修改系统变量(system variables)
mysql> set default_storage_engine=InnoDB;
Query OK, 0 rows affected (0.09 sec)
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
mysql>
3：如何查看表使用的存储引擎？
查看表所用的存储引擎，有下面几种方法：
3.1 查询information_schema.TABLES
mysql> SELECT TABLE_SCHEMA,
-> TABLE_NAME,
-> TABLE_TYPE,
-> ENGINE
-> FROM information_schema.TABLES
-> WHERE TABLE_NAME = 'TEST';
+--------------+------------+------------+--------+
| TABLE_SCHEMA | TABLE_NAME | TABLE_TYPE | ENGINE |
+--------------+------------+------------+--------+
| gsp | TEST | BASE TABLE | InnoDB |
+--------------+------------+------------+--------+
1 row in set (0.00 sec)
mysql>
3.2 使用SHOW CREATE TABLE TEST G命令。
mysql> SHOW CREATE TABLE TEST G;
*************************** 1. row ***************************
Table: TEST
Create Table: CREATE TABLE `TEST` (
`ID` int(11) DEFAULT NULL,
`COL1` varchar(6) DEFAULT NULL,
`COL2` varchar(6) DEFAULT NULL,
`COL3` varchar(6) DEFAULT NULL,
`COL4` varchar(6) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
3.3 SHOW TABLE STATUS
mysql> SHOW TABLE STATUS WHERE Name='TEST';
ERROR 1046 (3D000): No database selected
mysql>
mysql>
mysql> use gsp;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> SHOW TABLE STATUS WHERE Name='TEST';
如上所示，这种写法必须制定数据库，否则，你只能使用下面语法
SHOW TABLE STATUS [{FROM | IN} db_name]
[LIKE 'pattern' | WHERE expr]
mysql> SHOW TABLE STATUS FROM gsp WHERE Name='TEST';
4：如何修改相关表的存储引擎？
修改表的存储引擎非常简单，语法如下所示
ALTER TABLE my_table ENGINE = InnoDB;
mysql> ALTER TABLE TEST ENGINE=MyISAM;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW CREATE TABLE TEST G;
*************************** 1. row ***************************
Table: TEST
Create Table: CREATE TABLE `TEST` (
`ID` int(11) DEFAULT NULL,
`COL1` varchar(6) DEFAULT NULL,
`COL2` varchar(6) DEFAULT NULL,
`COL3` varchar(6) DEFAULT NULL,
`COL4` varchar(6) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
5：创建表的时候如何指定存储引擎。
创建表的时候，如果要指定存储引擎，只需要设置参数ENGINE即可。非常简单。
mysql> CREATE TABLE TEST1 (ID INT) ENGINE=InnoDB;
Query OK, 0 rows affected (0.02 sec)
mysql> CREATE TABLE TEST2 (ID INT) ENGINE=MyISAM;
Query OK, 0 rows affected (0.00 sec)
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