1. 背景
* 本地MySQL数据库要访问远程MySQL数据库的表中的数据, 必须通过FEDERATED存储引擎来实现.
* 有点类似Oracle中的数据库链接(DBLINK). 要允许这个存储引擎, 当构建MySQL时使用--with-federated-storage-engine来configure.
* 当创建一个FEDERATED表的时候, 服务器在数据库目录创建一个表定义文件. 文件由表的名字开始, 并有一个.frm扩展名.
* 无其它文件被创建, 因为实际的数据在一个远程数据库上.
2. 相关特性
* 允许本地访问远程 MySQL 数据库中表的数据
* 本地不存储任何数据文件
* 仅支持 MySQL 对 MySQL 的访问
* 不支持异构数据库的访问
* MySQL默认不开启Federated存储引擎
3. 环境
两个MySQL 5.7实例
serverA 3306
serverB 3307
[root@MySQL ~]# mysql -S /tmp/mysql.sock1 -p123456 mysql: [Warning] Using a password on the command line interface can be insecure. Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 7 Server version: 5.7.18 MySQL Community Server (GPL) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select version(); +-----------+ | version() | +-----------+ | 5.7.18 | +-----------+ 1 row in set (0.00 sec) [root@MySQL ~]# mysql -S /tmp/mysql.sock2 -p123456 mysql: [Warning] Using a password on the command line interface can be insecure. Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 6 Server version: 5.7.18 MySQL Community Server (GPL) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select version(); +-----------+ | version() | +-----------+ | 5.7.18 | +-----------+ 1 row in set (0.00 sec)
4. Federated存储引擎设置
* 查看Federated是否开启 [ FEDERATED 中Support状态NO表明引擎未开启 ]
mysql> show engines; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | CSV | YES | CSV storage engine | NO | NO | NO | | 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 | | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | | PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO | | ARCHIVE | YES | Archive storage engine | NO | NO | NO | | MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ 9 rows in set (0.01 sec)
* 配置文件指定开启Federated存储引擎 [ /etc/my.cnf ]
[mysqld] federated
* 重启MySQL 再次查看 [ FEDERATED 中Support状态成YES表明引擎开启成功 ]
mysql> show engines; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | CSV | YES | CSV storage engine | NO | NO | NO | | 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 | | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | | PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO | | ARCHIVE | YES | Archive storage engine | NO | NO | NO | | MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | FEDERATED | YES | Federated MySQL storage engine | NO | NO | NO | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ 9 rows in set (0.00 sec)
5. 部署
* 在ServerA上有一个数据库dbtestA，在ServerB上有数据库dbtestB，要在ServerB的数据库dbtestB上建立ServerA的数据库dbtestA上的表tabletestA的数据表链接remote_tabletestA，通过普通用户test连接。
* ServerA创建数据库
mysql> create database dbtestA; Query OK, 1 row affected (0.02 sec)
* ServerA在dbtestA数据库中创建tabletestA表
mysql> create table tabletestA( id INT PRIMARY KEY NOT NULL AUTO_INCREMENT )ENGINE=INNODB; Query OK, 0 rows affected (0.11 sec)
* ServerA中创建普通用户并授权dbtestA数据库相关权限
mysql> create user 'test'@'127.0.0.1' IDENTIFIED BY '123456'; Query OK, 0 rows affected (0.00 sec) mysql> grant select on dbtestA.* to 'test'@'127.0.0.1'; Query OK, 0 rows affected (0.00 sec)
* ServerB 中创建数据库 dbtestB
mysql> create database dbtestB; Query OK, 1 row affected (0.00 sec)
* ServerB 在dbtestB中创建链接表remote_tabletestA, 使用普通用户test
mysql> use dbtestB; Database changed mysql> create table remote_tabletestA( -> id INT PRIMARY KEY NOT NULL AUTO_INCREMENT -> )ENGINE=FEDERATED -> CONNECTION='mysql://test:123456@127.0.0.1:3306/dbtestA/tabletestA'; Query OK, 0 rows affected (0.09 sec)
* 在ServerA dbtestA库tableA表中插入数据
Database changed mysql> use dbtestA; Database changed mysql> insert into tabletestA select NULL; Query OK, 1 row affected (0.01 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> insert into tabletestA select NULL; Query OK, 1 row affected (0.03 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> insert into tabletestA select NULL; Query OK, 1 row affected (0.01 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> select * from tabletestA; +----+ | id | +----+ | 1 | | 2 | | 3 | +----+ 3 rows in set (0.01 sec)
* ServerB dbtestB库链接表remote_tabletestA查看
mysql> use dbtestB; Database changed mysql> select * from remote_tabletestA; +----+ | id | +----+ | 1 | | 2 | | 3 | +----+ 3 rows in set (0.01 sec)
* ServerB服务器中查看链接表remote_tablestestA相关文件
.frm 表定义文件 [ Federated链接库本地不产生数据文件 ]
[root@MySQL ~]# ll /data/mysql_data2/dbtestB/ total 16 -rw-r----- 1 mysql mysql 65 Jun 25 10:40 db.opt -rw-r----- 1 mysql mysql 8556 Jun 25 10:42 remote_tabletestA.frm
6. 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。
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