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！
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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。这里是创新互联，小编将为大家推送更多相关知识点的文章，欢迎关注！
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