如何使rails外部数据库调用？ [英] how to make rails external database calls?

问题描述

所以我想能够添加一个外部数据库到我的 config / database.yml 然后从它建模一个表。

So i'd like to be able to add an external database to my config/database.yml Then model one table from it.

这是可能吗？

连接到不同模型中的多个数据库

"Connection to multiple databases in different models

连接通常通过 ActiveRecord :: Base.establish_connection 创建，并由 ActiveRecord :: Base.connection 检索。 ActiveRecord :: Base 会使用这个连接，但你也可以设置一个特定类的连接，例如 Course 是 ActiveRecord :: Base ，但驻留在不同的数据库中，您只需说 Course.establish_connection code> Course ，所有的子类都将使用这个连接。

Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection. All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection. For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course.establish_connection and Course and all of its subclasses will use this connection instead.

code> ActiveRecord :: Base 这是一个由类索引的Hash如果请求连接，则retrieve_connection方法将向上爬到类层次结构，直到在连接池中找到连接。

This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool. "

推荐答案

首先，在database.yml中定义连接信息：

First, define the connection information in database.yml:

my_external_db:
  adapter: mysql
  username: ...
  ....

然后，创建模型并将其连接到外部db

Then, create the model and connect it to the external db

class MyExternalModel < ActiveRecord::Base
  establish_connection(:my_external_db)
  set_table_name 'my_external_table'
end

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