只在一个块中建立到另一个数据库的连接? [英] Establish a connection to another database only in a block?

问题描述

在 Rails 应用程序中，我有这个纯 ruby​​ 代码:

In a rails application, I have this code in pure ruby :

class LinkCreator
  attr_accessor :animal

  def initialize(animal:)
    @animal = animal
  end

  def call
    "something#{link_id}"
  end

  private

  def link_id
    connection.execute(sql_request).first.first
  end

  def sql_request
    "SELECT field FROM table WHERE field_id = '#{field_id}' LIMIT 1"
  end

  def field_id
    animal.field_id
  end

  def connection
    ActiveRecord::Base.establish_connection(
      adapter:  "mysql",
      host:     ENV["MYSQL_HOST"],
      username: ENV["MYSQL_USERNAME"],
      password: ENV["MYSQL_PASSWORD"],
      database: ENV["MYSQL_DB_NAME"]
    ).connection
  end
end

如您所见，这不是一个模型，而只是一个简单的类.问题是 activerecord 的连接发生了变化，其他请求稍后在新连接上执行.

As you can see, this is not a model but only a simple class. The problem is than the connection of activerecord is changed and the other requests, later, are executed on the new connection.

是否可以只在一个块中建立一个连接并回到旧的连接.我知道我可以建立另一个连接，但这对性能非常不利.

Is it possible to establish a connection only in a block and go back to the old connection. I know I can establish another connection but this is very bad for performance.

推荐答案

如果您将所有数据库连接都保存在 database.yml

It would be nice if you keep all database connections in database.yml

development:
  adapter: mysql2
  other stuff...
  
db_2:
  adapter: mysql2
  other stuff..

other_envs:
.....

然后创建一个类

class OtherDB < ActiveRecord::Base
  establish_connection(:db_2)
end

从你的控制器你可以像访问一样

From your controller you can access just like

OtherDB.table_name = "table_name"
OtherDB.first

在这里查看我的博客 http://imnithin.github.io/multiple-database.html

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