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这篇文章主要讲解了“怎么通过mysql的federated插件实现dblink功能”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“怎么通过mysql的federated插件实现dblink功能”吧！

db1：172.26.99.157 3306（源库）

db2：172.26.99.157 3310（通过dblink调用源库）

[root@node7 lepus]# mm

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 357

Server version: 5.7.29-log MySQL Community Server (GPL)

Copyright (c) 2000, 2020, 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> show engines;

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

| Engine | Support | Comment | Transactions | XA | Savepoints |

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

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

| 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 |

| MyISAM | YES | MyISAM storage engine | NO | NO | NO |

| ARCHIVE | YES | Archive storage engine | NO | NO | NO |

| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |

| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |

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

9 rows in set (0.00 sec)

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

ERROR 1125 (HY000): Function 'federated' already exists

mysql> exit

Bye

重启数据库，

# mysqladmin -uroot -P3310 -p -h 127.0.0.1 shutdown

# mysqld --defaults-file=/mysql/data/my.cnf --user=mysql --datadir=/mysql/data/3310 --basedir=/mysql/app/mysql --pid-file=/mysql/data/mysql3310.pid --socket=/mysql/data/mysql3310.sock --port=3310 &

在my.cnf中添加参数：

federated

mysql> show engines;

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

| Engine | Support | Comment | Transactions | XA | Savepoints |

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

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

| 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 |

| MyISAM | YES | MyISAM storage engine | NO | NO | NO |

| ARCHIVE | YES | Archive storage engine | NO | NO | NO |

| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |

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

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

9 rows in set (0.00 sec)

@3306：

# mysql -uroot -P3306 -h227.0.0.1 -p

mysql> create database testdb;

mysql> use testdb;

mysql> CREATE TABLE `options` (

-> `name` varchar(50) DEFAULT NULL,

-> `value` varchar(255) DEFAULT NULL,

-> `description` varchar(100) DEFAULT NULL,

-> KEY `idx_name` (`name`) USING BTREE

-> ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

@33310：

mysql> use tianlei;

mysql> CREATE TABLE `options` (

-> `name` varchar(50) DEFAULT NULL,

-> `value` varchar(255) DEFAULT NULL,

-> `description` varchar(100) DEFAULT NULL,

-> KEY `idx_name` (`name`) USING BTREE

-> ) ENGINE=FEDERATED DEFAULT CHARSET=utf8

-> CONNECTION='mysql://root:root123@172.26.99.157:3306/testdb/options';

Query OK, 0 rows affected (0.01 sec)

mysql> select * from options;

Empty set (0.01 sec)

@3306:

mysql>

mysql> insert into options (name,value ) values ('log','Y');

Query OK, 1 row affected (0.00 sec)

mysql> select * from options;

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

| name | value | description |

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

| log | Y | NULL |

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

1 row in set (0.00 sec)

@3310:

mysql> select * from options;

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

| name | value | description |

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

| log | Y | NULL |

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

1 row in set (0.00 sec)

mysql> insert into options (name,value ) values ('sql_mode','N');

Query OK, 1 row affected (0.01 sec)

mysql> select * from options;

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

| name | value | description |

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

| log | Y | NULL |

| sql_mode | N | NULL |

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

2 rows in set (0.00 sec)

mysql> update options set description='abc' where name='log';

Query OK, 1 row affected (0.01 sec)

Rows matched: 1 Changed: 1 Warnings: 0

mysql> delete from options where name ='sql_mode';

Query OK, 1 row affected (0.01 sec)

除了直接使用连接串的方法，还可以先创建server，然后建表时调用server：

还可以使用server的方式将连接串存储起来。

CREATE SERVER dblink

FOREIGN DATA WRAPPER mysql

OPTIONS (USER 'lepus', HOST '172.26.99.157', PORT 3306, DATABASE 'testdb');

CREATE TABLE `options2` (

`name` varchar(50) DEFAULT NULL,

`value` varchar(255) DEFAULT NULL,

`description` varchar(100) DEFAULT NULL,

KEY `idx_name` (`name`) USING BTREE

) ENGINE=FEDERATED

DEFAULT CHARSET=utf8

CONNECTION='dblink/options';

mysql> select * from options2;

ERROR 1429 (HY000): Unable to connect to foreign data source: Access denied for user 'lepus'@'172.26.99.157' (using password:

mysql> drop server dblink;

Query OK, 1 row affected (0.00 sec)

CREATE SERVER dblink

FOREIGN DATA WRAPPER mysql

OPTIONS (USER 'lepus', HOST '172.26.99.157', PORT 3306, DATABASE 'testdb',PASSWORD 'lepus');

mysql> CREATE SERVER dblink

-> FOREIGN DATA WRAPPER mysql

-> OPTIONS (USER 'lepus', HOST '172.26.99.157', PORT 3306, DATABASE 'testdb',PASSWORD 'lepus');

Query OK, 1 row affected (0.01 sec)

mysql> select * from options2;

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

| name | value | description |

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

| log | Y | abc |

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

1 row in set (0.01 sec)

mysql> show create table options2\G

*************************** 1. row ***************************

Table: options2

Create Table: CREATE TABLE `options2` (

`name` varchar(50) DEFAULT NULL,

`value` varchar(255) DEFAULT NULL,

`description` varchar(100) DEFAULT NULL,

KEY `idx_name` (`name`) USING BTREE

) ENGINE=FEDERATED DEFAULT CHARSET=utf8 CONNECTION='dblink/options'

1 row in set (0.00 sec)

在mysql 5.7官方文档中有federated引擎的具体介绍，地址为：

https://dev.mysql.com/doc/refman/5.7/en/federated-storage-engine.html

远程服务器中包括表定义和数据，可以是myisam、innodb或其他引擎；

本地服务器中只包括相同表结构的federated引擎表和远程服务器的连接串信息。增删改查操作都需要发到远程服务器中。

数据交互如下：

1.存储引擎查看FEDERATED表拥有的每一列，并构造引用远程表的适当SQL语句

2.语句使用MySQL客户端API发送到远程服务器

3.远程服务器处理语句，本地服务器检索语句产生的所有结果(受影响的行数或结果集)

4.如果语句生成了结果集，则每一列都转换为FEDERATED引擎所期望的内部存储引擎格式，并可用于向发出原始语句的客户端显示结果。

限制：

远端服务器必须是mysql

在调用前，FEDERATED指向的远端表必须存在

可以指向FEDERATED引擎表，注意不要循环嵌套

FEDERATED引擎无法使用索引，如果结果集很大，数据存放在内存中，可能使用大量swap甚至hang住。

FEDERATED引擎表支持insert、update、delete、select、truncate table操作和索引操作，但不支持alter table操作

能接受insert …… on deplicate key update,但不生效，有重复值仍然会报错

不支持事务

可以进行批量插入操作，但注意大小不要超过服务器建能传输的最大包大小

FEDERATED引擎表无法获知远程服务器上表的变化

使用连接串时，密码不能包括@符号

INSERT_id和时间戳选项不会传播到data provider

针对FEDERATED表发出的任何DROP TABLE语句只删除本地表，而不删除远程表

不使用查询缓存

不支持用户定义的分区

感谢各位的阅读，以上就是“怎么通过mysql的federated插件实现dblink功能”的内容了，经过本文的学习后，相信大家对怎么通过mysql的federated插件实现dblink功能这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是，小编将为大家推送更多相关知识点的文章，欢迎关注！