admins use statistic: reduce sql time

app/queries/admins/user_statistic_query.rb

@@ -46,12 +46,12 @@ class Admins::UserStatisticQuery < ApplicationQuery
       finish_challenge = finish_challenge.where(updated_at: time_range)
     end
 
-    study_myshixun_map   = study_myshixun.group(:user_id).count
-    finish_myshixun_map  = finish_myshixun.group(:user_id).count
-    study_challenge_map  = study_challenge.group(:user_id).count
-    finish_challenge_map = finish_challenge.group(:user_id).count
-    evaluate_count_map   = study_challenge.group(:user_id).sum(:evaluate_count)
-    cost_time_map        = study_challenge.group(:user_id).sum(:cost_time)
+    study_myshixun_map   = study_myshixun.reorder(nil).group(:user_id).count
+    finish_myshixun_map  = finish_myshixun.reorder(nil).group(:user_id).count
+    study_challenge_map  = study_challenge.reorder(nil).group(:user_id).count
+    finish_challenge_map = finish_challenge.reorder(nil).group(:user_id).count
+    evaluate_count_map   = study_challenge.reorder(nil).group(:user_id).sum(:evaluate_count)
+    cost_time_map        = study_challenge.reorder(nil).group(:user_id).sum(:cost_time)
 
     users.each do |user|
       user._extra_data = {