Rails 按一天中的小时对created_at 列进行分组

Question

我有一个Subscribe Model并且想按一天中的小时进行分组。我按 created_at和rails的日期检查了rails组记录- 按天和小时分组但没有运气！

2.3.0 :175 > Subscribe.find 13
  Subscribe Load (0.9ms)  SELECT  "subscribes".* FROM "subscribes" WHERE "subscribes"."id" = $1 LIMIT 1  [["id", 13]]
 => #<Subscribe id: 13, user_id: 7, publisher_id: 5, created_at: "2015-11-23 00:37:49", updated_at: "2016-03-22 08:04:31", subscription_id: "2"> 

关于应用其他解决方案

2.3.0 :174 > Subscribe.where("DATE_PART('hour', created_at) = ?", 13)
  Subscribe Load (1.0ms)  SELECT "subscribes".* FROM "subscribes" WHERE (DATE_PART('hour', created_at) = 13)
 => #<ActiveRecord::Relation []> 

为了实现这一点，我使用了groupdate

graph_data =  Subscribe.group_by_hour_of_day(:created_at, format: "%-l %M %P", time_zone: "Kolkata",range: start_date.to_datetime..end_date.to_datetime).count

 => {"12 00 am"=>0, "1 00 am"=>0, "2 00 am"=>0, "3 00 am"=>0, "4 00 am"=>0, "5 00 am"=>1, "6 00 am"=>1, "7 00 am"=>0, "8 00 am"=>0, "9 00 am"=>0, "10 00 am"=>0, "11 00 am"=>0, "12 00 pm"=>1, "1 00 pm"=>1, "2 00 pm"=>0, "3 00 pm"=>0, "4 00 pm"=>0, "5 00 pm"=>0, "6 00 pm"=>0, "7 00 pm"=>0, "8 00 pm"=>0, "9 00 pm"=>0, "10 00 pm"=>0, "11 00 pm"=>0} 

但对于 Subscribe 13，created_at (2015-11-23 00:37:49) 有一条记录，但它返回 0

任何帮助，将不胜感激！！！

Answer 1

尝试

Subscribe.all.group_by{ |s| s.created_at.hour }