Question

我有以下型号

App has_many features
Feature has_many translations

现在我想查找翻译，看看是否需要创建或更新。

    App.joins(features: :translations).first.features.each do |feature|
      languages.each do |lang|
        translation = feature.translations.where(language: lang).first_or_initialize
    end
   end

现在问题是我对每种语言都有一个数据库查找，这是一个很大的问题，因为我有很多功能。如何在加入表中查找翻译时，如何从预先加载中受益？

Answer 1

让我们将语言分成两个数组：found和not_found：

 found, not_found = languages.partition do |lang| 
   App.joins(:features => :translations).where("translations.language" => lang).present?
 end

 found_language_translations = Translation.where("language in (?)", found)
 new_language_translations = not_found.map{|lang| Translation.new(language: lang) } #This will fire up too many queries though :/

如何在连接表上执行where where where而不在循环中查询db

1 个答案: