无法使用 Mobility 按 Rails 中翻译的列进行排序

这个问题是基于一个issue https://github.com/shioyama/mobility/issues/169发布到 Mobility GitHub 项目。

Context

• Rails: 5.0.6
• Mobility：0.4.2（带表后端）

我正在使用支持多种文章类型（例如博客文章、案例研究、知识库文章）的文章表。该表包含一个用于跟踪文章被查看次数的列，这是一个整数列，每次查看次数都会增加show文章需要采取行动。

在实现这些文章的翻译时，我想跟踪浏览量每个翻译单独，不适用于主要文章对象。为了实现这一目标，我将views属性作为我的对象的翻译属性之一：

class Article < ApplicationRecord
  include Taggable
  include PgSearch

  translates :title, type: :string
  translates :subtitle, type: :text
  translates :body, type: :text
  translates :views, type: :integer

  multisearchable :against => [:title, :subtitle, :body]

  has_and_belongs_to_many :products

  attachment :hero_image, content_type: %w(image/jpeg image/png image/gif)

  validates :title, :body, :posted_on, presence: true

  scope :current, -> { where 'posted_on < ?', Date.tomorrow }
  scope :news_articles, -> { where type: ['BlogPost', 'CaseStudy'] }

  def log_view(by = 1)
    self.views ||= 0
    self.views += by
    self.save(touch: false)
  end

  def to_param
    "#{id} #{title}".parameterize
  end

  def published?
    posted_on < Date.tomorrow
  end
end

预期行为

在我的控制器中，我想列出浏览次数最多的十篇文章，这是通过以下查询获得的：

@top_articles = Article.current.news_articles.order(views: :desc, posted_on: :desc).limit(10)

我希望收到一系列文章，就像我在实施 Mobility 之前所做的那样。

实际行为

我得到的是#<Article::ActiveRecord_Relation:0x233686c>。如果我然后尝试将其转换为数组@top_articles.to_a，我收到此错误：

  Article Load (0.7ms)  SELECT  "articles".* FROM "articles" WHERE (posted_on < '2018-02-11') AND "articles"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"."views" DESC, "articles"."posted_on" DESC LIMIT $1  [["LIMIT", 10]]
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR:  column articles.views does not exist
LINE 1: ...les"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"...
                                                             ^
: SELECT  "articles".* FROM "articles" WHERE (posted_on < '2018-02-11') AND "articles"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"."views" DESC, "articles"."posted_on" DESC LIMIT $1
from /usr/local/bundle/gems/activerecord-5.0.6/lib/active_record/connection_adapters/postgresql_adapter.rb:598:in `async_exec'

更改查询以包含i18n:

@top_articles = Article.i18n.current.news_articles.order(views: :desc, posted_on: :desc).limit(10)

…返回#<#<Mobility::Backends::ActiveRecord::Table::QueryMethods:0x00000000050a86d8>:0x286c3e0>，当我尝试将其转换为数组时，我得到同样的结果：

  Article Load (0.7ms)  SELECT  "articles".* FROM "articles" WHERE (posted_on < '2018-02-11') AND "articles"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"."views" DESC, "articles"."posted_on" DESC LIMIT $1  [["LIMIT", 10]]
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR:  column articles.views does not exist
LINE 1: ...les"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"...
                                                             ^
: SELECT  "articles".* FROM "articles" WHERE (posted_on < '2018-02-11') AND "articles"."type" IN ('BlogPost', 'CaseStudy') ORDER BY "articles"."views" DESC, "articles"."posted_on" DESC LIMIT $1
from /usr/local/bundle/gems/activerecord-5.0.6/lib/active_record/connection_adapters/postgresql_adapter.rb:598:in `async_exec'

事实证明，虽然 Mobility 支持在where条款，目前不支持它们orderActive Record 查询的子句。

解决方法尝试

1. 参考翻译表order clause

根据 gem 作者的反馈，我尝试了以下查询：

Article.i18n.current.news_articles.order('article_translations.views desc', 'articles.posted_on desc')

...它返回一个#<#<Mobility::Backends::ActiveRecord::Table::QueryMethods>>对象，以及to_a返回此错误：

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "article_translations"
LINE 1: ...les"."type" IN ('BlogPost', 'CaseStudy') ORDER BY article_tr...
                                                             ^
: SELECT  "articles".* FROM "articles" WHERE (posted_on < '2018-02-12') AND "articles"."type" IN ('BlogPost', 'CaseStudy') ORDER BY article_translations.views desc, articles.posted_on desc LIMIT $1
from /usr/local/bundle/gems/activerecord-5.0.6/lib/active_record/connection_adapters/postgresql_adapter.rb:598:in `async_exec'

2.添加一个joins or includes翻译表的子句

Article.i18n.joins(:article_translations).order('article_translations.views desc', 'articles.posted_on desc').limit(10)

该查询再次返回一个#<#<Mobility::Backends::ActiveRecord::Table::QueryMethods>>对象，以及to_a结果是：

ActiveRecord::ConfigurationError: Can't join 'Article' to association named 'article_translations'; perhaps you misspelled it?
from /usr/local/bundle/gems/activerecord-5.0.6/lib/active_record/associations/join_dependency.rb:231:in `find_reflection'

3. Add has_many :article_translations模拟

向模型添加关系会引发此错误：

uninitialized constant Article::ArticleTranslation

So…

接下来我应该尝试什么？

UPDATE

从版本 0.8.0/ 开始，现在支持按翻译属性排序

只需这样做：

Article.i18n.current.news_articles.
  order(:views => :desc, :'articles.posted_on' => :desc)

Mobility 将处理一切（您不需要加入翻译表等）

原答案

你是对的，你需要加入翻译表，但关联被命名为translations, not article_translations.

无论如何，有一个方法join_translations连接翻译表，所以这应该有效：

Article.i18n.
  current.
  news_articles.
  join_translations.
  order('article_translations.views desc', 'articles.posted_on desc')