Question

在我为项目添加更多关系后，我收到此跟踪错误。在localhost上，页面显示完全正常。但是，在尝试在heroku上查看时出现错误。

ActiveRecord::StatementInvalid (PG::Error: ERROR:  for SELECT DISTINCT, ORDER BY expressions must appear in select list

这是我的traveldeal控制器：

  def show
    @traveldeal = @commentable = Traveldeal.find(params[:id])
    @comments = Comment.all
    @title = @traveldeal.title
    @eventdeals = Eventdeal.tagged_with(@traveldeal.location_tag_list, :any => true, :order => 'RANDOM()', :limit => 3)
  end

traveldeal / show.html

<% unless @eventdeals.blank? %>

  <h1>Events in the area:</h1>

  <% @eventdeals.each do |eventdeal| %>
    <%= link_to eventdeal do %>
      <!-- content -->
    <% end %>
  <% end %>

<% end %>

Heroku记录

SELECT DISTINCT eventdeals.* FROM "eventdeals" JOIN taggings event_taggings_e9f0e2e ON event_taggings_e9f0e2e.taggable_id = eventdeals.id AND event_taggings_e9f0e2e.taggable_type = 'Eventdeal' WHERE (event_taggings_e9f0e2e.tag_id = 1 OR event_taggings_e9f0e2e.tag_id = 3 OR event_taggings_e9f0e2e.tag_id = 4 OR event_taggings_e9f0e2e.tag_id = 5) ORDER BY RANDOM()):

此代码正常运行，因此我只显示了3个与location（通过act-as-taggable-on）匹配traveldeal的随机eventdeals。

然而，在我添加了一个关系（与eventdeals相关但不是traveldeals）之后，我开始得到pg错误。

以下是添加的关系：

trip.rb

class Trip < ActiveRecord::Base
  has_many :eventdealtrips, :dependent => :destroy
  has_many :eventdeals, :through => :eventdealtrips
end

eventdeal.rb

class Eventdeal < ActiveRecord::Base
  has_many :eventdealtrips
  has_many :trips, :through => :eventdealtrips, :dependent => :destroy
end

eventdealtrip.rb

class Eventdealtrip < ActiveRecord::Base
  belongs_to :eventdeal
  belongs_to :trip
end

关于如何获得3个eventdeals的随机数组的任何建议？

感谢。

Answer 1

我遇到了这个问题，并通过在菊花链末端运行order解决了这个问题。

SELECT DISTINCT的PG错误，ORDER BY表达式在尝试在Heroku上查看时必须出现在选择列表中

1 个答案: