fix error

temp_file/app/models/site.rb

@@ -72,6 +72,9 @@ class Site
   mount_uploader :favicon, ImageUploader
   mount_uploader :mobile_icon, ImageUploader
   Impression.class_eval{
+    def self.create_date_for_group(date)
+      {'_id'=>{'year'=>date.year,'month'=>date.month,'day'=>date.day},'count'=>0}
+    end
     def self.group_by(field,day_limit,start_day=Date.today,format = 'day')
       limit_ele = self.desc(:id).where({ created_at: { "$lt" => start_day-(day_limit-2).days }}).first || self.first
       key_op = [['year','$year'],['month', '$month'], ['day', '$dayOfMonth']]
@@ -84,7 +87,11 @@ class Site
           {"$group" => {"_id" => group_id_fields,"count" => {"$sum" => 1}}},
           {"$sort" => {"_id"=>-1}}
       ]
-      collection.aggregate(pipeline)
+      tmp = collection.aggregate(pipeline)
+      if tmp.count < day_limit
+        tmp.concat(Array.new(day_limit-tmp.count).map.with_index.map{|v,i| create_date_for_group(start_day+i.days)})
+      end
+      tmp
     end
   }
   after_initialize do