Rails 3 - 具有连接条件的多个数据库 [英] Rails 3 - Multiple database with joins condition

问题描述

我的环境：Ruby 1.9.2p290，Rails 3.0.9和RubyGem 1.8.8

多个数据库。

情况是这样：我有两个模型连接两个不同的数据库，并建立彼此之间的关联。
数据库连接在每个模型中指定，看起来像

  ActiveRecord :: Base 
 self.establish_connectionlab
 belongs_to：patient 
 end 
 
 class Patient< ActiveRecord :: Base 
 self.establish_connectionmain
 has_many：visits 
 end 
  

遇到以下情况时出现错误

  @visits = Visit.joins（：patient）
  

错误：Mysql2 ::错误：表'lab.patients'不存在：SELECT 访问。* FROM 访问 INNER JOIN 患者 ON 患者。 id IS NULL

这里'patients'表位于'main'和'visits'表在'lab'数据库
我怀疑当执行代码，Rails正在考虑'病人'表是'实验室'数据库[其中包含访问表的一部分。

$好吧，我不知道这是最优雅的解决方案，但我确实得到这个工作通过定义 self.table_name_prefix 以显式返回数据库名称。

  class Visit< ActiveRecord :: Base 
 def self.table_name_prefix 
 renv = ENV ['RAILS_ENV'] || ENV ['RACK_ENV'] 
（renv.empty？？lab。：lab _＃{renv}。）
 end 
 
 self.establish_connectionlab
 belongs_to：patient 
 end 
 
 class Patient< ActiveRecord :: Base 
 def self.table_name_prefix 
 renv = ENV ['RAILS_ENV'] || ENV ['RACK_ENV'] 
（renv.empty？？main。：main _＃{renv}。）
 end 
 
 self.establish_connectionmain
 has_many：visits 
 end 
  

我仍在处理所有细节它涉及到指定加入条件，但我希望这有助于。

My environment: Ruby 1.9.2p290, Rails 3.0.9 and RubyGem 1.8.8

unfortunately I have an issue when come across multiple database.

The situation is this: I have two model connect with two different database and also establishing association between each other. database connection specifying in each model, look likes

class Visit < ActiveRecord::Base
  self.establish_connection "lab"
  belongs_to :patient
end

class Patient < ActiveRecord::Base
  self.establish_connection "main"
  has_many :visits
end

I got an error when meet following scenario

@visits = Visit.joins(:patient)

Errors: Mysql2::Error: Table 'lab.patients' doesn't exist: SELECT visits.* FROM visits INNER JOIN patients ON patients.id IS NULL

Here 'patients' table is in 'main' database and 'visits' table in 'lab' database I doubt when executing the code, that Rails is considering 'patients' table is part of 'lab' database [which holds 'visits' table].

解决方案

Well, I don't know if this is the most elegant solution, but I did get this to work by defining self.table_name_prefix to explicitly return the database name.

class Visit < ActiveRecord::Base
  def self.table_name_prefix
    renv = ENV['RAILS_ENV'] || ENV['RACK_ENV']
    (renv.empty? ? "lab." : "lab_#{renv}.")
  end

  self.establish_connection "lab"
  belongs_to :patient
end

class Patient < ActiveRecord::Base
  def self.table_name_prefix
    renv = ENV['RAILS_ENV'] || ENV['RACK_ENV']
    (renv.empty? ? "main." : "main_#{renv}.")
  end

  self.establish_connection "main"
  has_many :visits
end

I'm still working through all the details when it comes to specifying the join conditions, but I hope this helps.

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