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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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | 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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | 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：
1 2 3 | mysql> alter table wholesale engine=innodb;Query OK, 1 row affected (0.32 sec)Records: 1 Duplicates: 0 Warnings: 0 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | 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：
1 2 3 | # mysqldump -uroot -p123456 sx >sx_bak.sqlsed -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）
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