Ruby on rails 使用Rails时出现Postgresql错误'；uniq法

我有一个

项目

模型，它属于

产品

模型<代码>产品有一个hstore类型的

属性

列。我想返回一组属于某个产品且不包括当前项目的唯一

项目

：

@item。类似的\u项目

class Item < ActiveRecord::Base
  belongs_to :product
  scope :by_platform, ->(value) { joins(:product).merge(Product.by_platform(value)) }
  scope :by_genre, ->(value) { joins(:product).merge(Product.by_genre(value)) }

  def similar_items
    Item.includes(:product)
      .by_platform(self.product_platform)
      .by_genre(self.product_genre)
      .limit(3).where.not(product: self.product)
      .order("(properties -> 'release_date')::date DESC")
      .uniq
  end
end

class Product < ActiveRecord::Base
  store_accessor :properties, :platform, :genre
  has_many :items

  scope :by_platform, ->(value) { where("properties @> hstore('platform', ?)", value) }
  scope :by_genre, ->(value) { where("properties @> hstore('genre', ?)", value) }
end

---

正如错误消息所述

test=> select distinct id from test order by f;
ERROR:  for SELECT DISTINCT, ORDER BY expressions must appear in select list
LINE 1: select distinct id from test order by f;

---

将您的排序列添加到语句的select部分。

错误消息指出

test=> select distinct id from test order by f;
ERROR:  for SELECT DISTINCT, ORDER BY expressions must appear in select list
LINE 1: select distinct id from test order by f;

将排序列添加到语句的select部分