rails 连接多个数据库 / multiple databases

October 31, 2017

• refer to
  • http://api.rubyonrails.org/classes/ActiveRecord/Base.html

Connection to multiple databases in different models

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.

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 ActiveRecord::Base.retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.

例子，redmine 连接 testlink 数据库

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# app/models/xc_testlink/base_object.rb
module XcTestlink
  #
  # 所有 Testlink model的父类
  # 子类中指明表名： self.table_name = "testplans"
  #
  class BaseObject < ActiveRecord::Base
    self.establish_connection :testlink
    self.abstract_class = true
  end
end

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# app/models/xc_testlink/testplan.rb
module XcTestlink
  #
  # Test Plan
  #
  class Testplan < BaseObject
    self.table_name = "testplans"
  end
end

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config/database.yml
testlink:
  adapter: mysql2
  database: testlink
  host: localhost
  username: testlink
  password: 2013Pwd
  encoding: utf8