业务上有需求,需要跨服务器跨数据库的多表查询,然后想到了两个办法:
- 分开查询,就是先把半成品的结果记录下来,然后做二次查询,这是一个笨办法
- federated存储引擎
一.什么是federated引擎?
ederated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。
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。
二.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
动态安装命令
mysql> install plugin federated soname ‘ha_federated.so’;
Query OK, 0 rows affected, 1 warning (0.02 sec)
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[mysqld]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。
三. federated的使用
这里假设有ip1上的数据DB1有个表为table1,而我需要在ip2上建立数据库DB2中建立相同的表:
先在ip1上:show create table table1;得到建表语句。
然后跑到ip2服务器上
使用FEDERATED建表语句如下:
CREATE TABLE (......) ENGINE =FEDERATED CONNECTION='mysql://[name]:[pass]@[location]:[port]/[db-name]/[table-name]'
创建成功后就可直接在本地查询相应的远程表了。
需要注意的几点:
1. 本地的表结构必须与远程的完全一样。
2.远程数据库目前仅限MySQL
3.不支持事务
4.不支持表结构修改