MySQL修改表的存储引擎(myisam<=>innodb)
MySQL修改表的存储引擎(myisam<=>innodb)
查看当前MySQL数据库的所支持的数据库引擎以及默认数据库引擎
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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
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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
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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：
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mysql> alter table wholesale engine=innodb;
Query OK, 1 row affected (0.32 sec)
Records: 1 Duplicates: 0 Warnings: 0
|
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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：
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# 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）本文永久更新链接地址：
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