Ruby on rails 为什么ActiveRecord不接收这些获取聚合函数

直接在带有Postgres的ActiveRecord上使用聚合函数进行查询似乎可以正常工作

ActiveRecord::Base.connection.execute("
  SELECT created_at::date as date, 
    sum(item1_count) as sum_item1, 
    sum(item2_count) as sum_item2,
    sum(item3) as sum_item3 from items 
  GROUP by 
    created_at::date ORDER BY date desc").to_a

返回类似这样的值，这是可以的

[
  {
              "date" => "2014-01-23",
         "sum_item1" => "3239",
        "sum_item2" => "90",
      "sum_item3" => "0.00000"
  },
  {
              "date" => "2014-01-22",
         "sum_item1" => "1981",
        "sum_item2" => "19",
      "sum_item3" => "0.00000"
  }
]

例如，问题是当尝试使用作用域执行相同操作时

class Item < ActiveRecord::Base
  scope :myscope, -> { 
    select("created_at::date as date, sum(item1_count) as sum_item1, 
      sum(item2_count) as sum_item2, 
      sum(item3) as sum_item3")
   .group("created_at::date")
   .order("date desc") }
end

---

如何将聚合函数传递给作用域？

我可能有点不对劲，但我记得必须将聚合字段名用引号括起来，例如selectsumitem1\u count as'sum\u item1'尝试过，但似乎没有什么不同。您是否尝试过对对象调用聚合方法来检查它是否存在？像Item.first.sum_item2一样，我只是做了一个快速测试，即使对象检查器没有打印出聚合字段，它们仍然存在，并且调用它们的方法返回正确的值。

[
  #<Item:0x00000103cc3d38> {
      :id => nil,
    :date => Thu, 23 Jan 2014
  },
  #<Item:0x00000103cc39a0> {
      :id => nil,
    :date => Wed, 22 Jan 2014
  }
]