1. 背景
* InnoDB的表空间可以是共享的或独立的。如果是共享表空间,则所有的表空间都放在一个文件里:ibdata1,ibdata2..ibdataN,这种情况下,目前应该还没办法实现表空间的迁移,除非完全迁移。
* 不管是共享还是独立表空间,InnoDB每个数据表的元数据(metadata)总是保存在 ibdata1 这个共享表空间里,因此该文件必不可少,它还可以用来保存各种数据字典等信息。
* 独立表空间中数据文件单独存放在.ibd文件中。
* MySQL 5.6版本开始支持独立表空间导入与导出。
2. 环境 [ 2台DB实例, MySQL 5.6表迁移至MySQL5.7 ]
* 源实例 MySQL
mysql> show variables like 'innodb%version'; +----------------+--------+ | Variable_name | Value | +----------------+--------+ | innodb_version | 5.6.36 | +----------------+--------+ 1 row in set (0.01 sec) mysql> show variables like 'datadir'; +---------------+--------------------+ | Variable_name | Value | +---------------+--------------------+ | datadir | /data/mysql_data6/ | +---------------+--------------------+ 1 row in set (0.00 sec)
* 目的实例 MySQL
mysql> show variables like 'innodb%version'; +----------------+--------+ | Variable_name | Value | +----------------+--------+ | innodb_version | 5.7.18 | +----------------+--------+ 1 row in set (0.00 sec) mysql> show variables like 'datadir'; +---------------+--------------------+ | Variable_name | Value | +---------------+--------------------+ | datadir | /data/mysql_data7/ | +---------------+--------------------+ 1 row in set (0.01 sec)
* 源实例 MySQL 迁移的数据库与表信息
mysql> select database(); +------------+ | database() | +------------+ | mytest | +------------+ 1 row in set (0.00 sec) mysql> show create table users; +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | users | CREATE TABLE `users` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, `sex` enum('M','F') NOT NULL DEFAULT 'M', `age` int(11) NOT NULL DEFAULT '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 | +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.01 sec) mysql> select * from users; +----+-------+-----+-----+ | id | name | sex | age | +----+-------+-----+-----+ | 1 | tom | M | 25 | | 2 | jak | F | 38 | | 3 | sea | M | 43 | | 4 | lisea | M | 36 | +----+-------+-----+-----+ 4 rows in set (0.00 sec)
3. 平滑迁移实战 [ 迁移mytest数据库下users表 ]
* 目的MySQL实例创建相同的数据库与表 [ MySQL 5.7中创建表需要指定row_format=compact ]
mysql> create database mytest character set utf8mb4; Query OK, 1 row affected (0.03 sec) mysql> use mytest; Database changed mysql> CREATE TABLE `users` ( -> `id` bigint(20) NOT NULL AUTO_INCREMENT, -> `name` varchar(255) NOT NULL, -> `sex` enum('M','F') NOT NULL DEFAULT 'M', -> `age` int(11) NOT NULL DEFAULT '0', -> PRIMARY KEY (`id`) -> ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 row_format=compact; Query OK, 0 rows affected (0.59 sec) mysql> system ls -l /data/mysql_data7/mytest/ total 64 -rw-r----- 1 mysql mysql 67 Jul 18 05:21 db.opt -rw-r----- 1 mysql mysql 8648 Jul 18 05:21 users.frm -rw-r----- 1 mysql mysql 49152 Jul 18 05:21 users.ibd
* 目的MySQL实例丢弃表空间
mysql> alter table users discard tablespace; Query OK, 0 rows affected (0.01 sec) mysql> system ls -l /data/mysql_data7/mytest/ total 16 -rw-r----- 1 mysql mysql 67 Jul 18 05:21 db.opt -rw-r----- 1 mysql mysql 8648 Jul 18 05:21 users.frm
* 源MySQL实例刷新表至磁盘并加lock,并且当前表quiesce状态,只读,且创建.cfg metadata文件
mysql> flush tables users for export; Query OK, 0 rows affected (0.00 sec)
* 从源MySQL实例服务止拷贝表文件users.ibd, users.cfg文件至目的MySQL实例中
[root@MySQL ~]# cp -v /data/mysql_data6/mytest/users.{cfg,ibd} /data/mysql_data7/mytest/ `/data/mysql_data6/mytest/users.cfg' -> `/data/mysql_data7/mytest/users.cfg' `/data/mysql_data6/mytest/users.ibd' -> `/data/mysql_data7/mytest/users.ibd'
* 修改目的MySQL实例数据文件下拷贝文件的所有者与所有组
[root@MySQL ~]# chown -v mysql.mysql /data/mysql_data7/mytest/users.{cfg,ibd} changed ownership of `/data/mysql_data7/mytest/users.cfg' to mysql:mysql changed ownership of `/data/mysql_data7/mytest/users.ibd' to mysql:mysql
* 源MySQL实例释放lock
mysql> unlock tables; Query OK, 0 rows affected (0.00 sec)
* 目的MySQL实例加载表空间
mysql> alter table users import tablespace; Query OK, 0 rows affected (0.04 sec)
* 查看目的MySQL实例表数据 [ MySQL5.6数据成功迁移过来 ]
mysql> select * from users; +----+-------+-----+-----+ | id | name | sex | age | +----+-------+-----+-----+ | 1 | tom | M | 25 | | 2 | jak | F | 38 | | 3 | sea | M | 43 | | 4 | lisea | M | 36 | +----+-------+-----+-----+ 4 rows in set (0.00 sec)
4. 注意问题
* MySQL 5.6数据迁移到MySQL5.7时,如果创建目的表时不指定row_format,import表数据时会报错,原因在于MySQL 5.6中是Antelope,在MySQL 5.7中是Barracuda,主要是在表压缩和行的动态格式上有所改变。
5. 总结
以需求驱动技术,技术本身没有优略之分,只有业务之分。