mysql修改表的存储引擎(myisam<=>innodb)

查看当前数据库的所支持的数据库引擎以及默认数据库引擎

mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)

 查看表的存储引擎

mysql> show tables;
+----------------------------------------------+
| Tables_in_performance_schema                 |
+----------------------------------------------+
| cond_instances                               |
| events_waits_current                         |
| events_waits_history                         |
| events_waits_history_long                    |
| events_waits_summary_by_instance             |
| events_waits_summary_by_thread_by_event_name |
| events_waits_summary_global_by_event_name    |
| file_instances                               |
| file_summary_by_event_name                   |
| file_summary_by_instance                     |
| mutex_instances                              |
| performance_timers                           |
| rwlock_instances                             |
| setup_consumers                              |
| setup_instruments                            |
| setup_timers                                 |
| threads                                      |
+----------------------------------------------+
17 rows in set (0.00 sec)

mysql> show create table threads;
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table   | Create Table                                                                                                                                                                      |
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| threads | CREATE TABLE `threads` (
  `THREAD_ID` int(11) NOT NULL,
  `PROCESSLIST_ID` int(11) DEFAULT NULL,
  `NAME` varchar(128) NOT NULL
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8 |
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

 直接更改存储引擎

mysql> show create table wholesale;
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table             | Create Table                                                                                                                                                                                                                                                                                                                                                                                                      |
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| jindong_wholesale | CREATE TABLE `wholesale` (
  `act_id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
  `goods_id` mediumint(8) unsigned NOT NULL,
  `goods_name` varchar(255) NOT NULL,
  `rank_ids` varchar(255) NOT NULL,
  `prices` text NOT NULL,
  `enabled` tinyint(3) unsigned NOT NULL,
  PRIMARY KEY (`act_id`),
  KEY `goods_id` (`goods_id`) USING BTREE
) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 |
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

 如下命令：

mysql> alter table wholesale engine=innodb;
Query OK, 1 row affected (0.32 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> show create table wholesale;
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table             | Create Table                                                                                                                                                                                                                                                                                                                                                                                                      |
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| jindong_wholesale | CREATE TABLE `wholesale` (
  `act_id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
  `goods_id` mediumint(8) unsigned NOT NULL,
  `goods_name` varchar(255) NOT NULL,
  `rank_ids` varchar(255) NOT NULL,
  `prices` text NOT NULL,
  `enabled` tinyint(3) unsigned NOT NULL,
  PRIMARY KEY (`act_id`),
  KEY `goods_id` (`goods_id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 |
+-------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

 多表改变引擎：

# mysqldump -uroot -p123456 sx >sx_bak.sql
sed -i "s/MyISAM/InnoDB/g" sx_bak.sql
 mysql -uroot -p123456 sx <sx_bak.sql

 首先我目前平台上承载的大部分项目是读多写少的项目，而MyISAM的读性能是比Innodb强不少的。

MyISAM的索引和数据是分开的，并且索引是有压缩的，内存使用率就对应提高了不少。能加载更多索引，而Innodb是索引和数据是紧密捆绑的，没有使用压缩从而会造成Innodb比MyISAM体积庞大不小。

从我接触的应用逻辑来说，select count(*) 和order by 是最频繁的，大概能占了整个sql总语句的60%以上的操作，而这种操作Innodb其实也是会锁表的，很多人以为Innodb是行级锁，那个只是 where对它主键是有效，非主键的都会锁全表的。

 还有就是经常有很多应用部门需要我给他们定期某些表的数据，MyISAM的话很方便，只要发给他们对应那表的frm.MYD,MYI的文件，让他们自己在 对应版本的数据库启动就行，而Innodb就需要导出xxx.sql了，因为光给别人文件，受字典数据文件的影响，对方是无法使用的

如果和MyISAM比insert写操作的话，Innodb还达不到MyISAM的写性能，如果是针对基于索引的update操作，虽然MyISAM可能会逊色Innodb,但是那么高并发的写，从库能否追的上也是一个问题，还不如通过多实例分库分表架构来解决

MyISAM 相对更适合插入不多不频繁，查询较多的应用环 WAL(write ahead logging)

InnoDB适合大并发写入和查询的环境：支持事务（ACID 空间（不受大文件限制）

http://www.cnblogs.com/littlehb/archive/2013/04/20/3032658.html

http://blog.163.com/yang_jianli/blog/static/161990006201010175122563/

http://www.cnblogs.com/littlehb/archive/2013/04/20/3032658.html