安装federated存储引擎

Federated存储引擎可以使你在本地数据库中访问远程数据库中的数据，针对federated存储引擎表的查询会被发送到远程数据库的表上执行，本地是不存储任何数据的。

简要介绍后，是不是发现它和Oracle的database link(数据库链接)非常相似，它所实现的功能和db link类似，要在MySQL下找寻db link替代品的，federated存储引擎是不二的选择。

1.   查看当前支持的存储引擎

SQL>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         |

| 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        |

| MyISAM     | YES     | Default engine as of MySQL 3.23 with great performance     | NO           | NO   | NO         |

+------------+---------+------------------------------------------------------------+--------------+------+------------+

5 rows in set (0.00 sec)

发现安装MySQL时没有编译进来，只能现安装了。

2.   安装federated存储引擎

由于编译时没有选择federated，所以打算通过INSTALL PLUGIN的方式安装，正常情况下，federated是支持动态安装的：

   === Federated Storage Engine ===

  Plugin Name:      federated

  Description:      Connects to tables on remote MySQL servers

  Supports build:   static and dynamic

  Configurations:   max, max-no-ndb

可是执行以下命令时报错：

SQL>install plugin federated soname 'ha_federated.so';

ERROR 1126 (HY000): Can't open shared library '/usr/local/mysql/lib/mysql/plugin/ha_federated.so' (errno: 2 undefined symbol: dynstr_append_mem)

搜了一下，发现是个老问题，竟然到现在都没解决，可见MySQL团队的效率和管理的混乱。http://bugs.mysql.com/bug.php?id=40942

没有办法了，只有重新编译MySQL源码了, 加上--with-plugins=federated。从 5.1.26 开始，默认MySQL不启用federated存储引擎，所以需要在my.cnf中加入federated选项或是在命令行用--federated选项启动mysqld。编译后的结果如下：

SQL>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         |

| FEDERATED  | YES     | Federated MySQL storage engine                                             | NO           | NO   | NO         |

| MyISAM     | YES     | Default engine as of MySQL 3.23 with great performance                     | NO           | NO   | NO         |

| InnoDB     | DEFAULT | Percona-XtraDB, Supports transactions, row-level locking, and foreign keys | YES          | YES  | YES        |

| MEMORY     | YES     | Hash based, stored in memory, useful for temporary tables                  | NO           | NO   | NO         |

+------------+---------+----------------------------------------------------------------------------+--------------+------+------------+

6 rows in set (0.00 sec)

至此，我们已经可以使用federated存储引擎了。