修改迁移文件

db/migrate/20150911064528_alter_user_activities.rb

@@ -1,21 +1,16 @@
 class AlterUserActivities < ActiveRecord::Migration
   def up
-    count = UserActivity.all.count / 30 + 3
-    transaction do
-      for i in 1 ... count do i
-        UserActivity.page(i).per(30).each do |activity|
-          if activity.act_type == 'Message'
-            if activity.act
-              unless activity.act.parent_id.nil?
-                parent_act = UserActivity.where("act_id = #{activity.act.parent.id} and act_type='Message'").first
-                parent_act.created_at = activity.act.parent.children.maximum("created_on")
-                parent_act.save
-                activity.destroy
-              end
-            else
-              activity.destroy
-            end
+    UserActivity.each do |activity|
+      if activity.act_type == 'Message'
+        if activity.act
+          unless activity.act.parent_id.nil?
+            parent_act = UserActivity.where("act_id = #{activity.act.parent.id} and act_type='Message'").first
+            parent_act.created_at = activity.act.parent.children.maximum("created_on")
+            parent_act.save
+            activity.destroy
           end
+        else
+          activity.destroy
         end
       end
     end