diff --git a/app/serializers/collection_serializer.rb b/app/serializers/collection_serializer.rb
index 6df8b10ccd32c6d01dc33371e5284fe073100cea..36904b88abb280581edc8d255e5c904109409d67 100644
--- a/app/serializers/collection_serializer.rb
+++ b/app/serializers/collection_serializer.rb
@@ -13,7 +13,8 @@ class CollectionSerializer < ActiveModel::Serializer
     object.complained? current_user
   end
 
-  attributes :id, :name, :owner, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :reviewed, :complained, :review_average, :thumbnail
+  attributes :id, :name, :created_at, :updated_at, :description, :privacy, :score, :likes_count, :liked, :reviewed, :complained, :review_average, :thumbnail
+  belongs_to :owner
   has_many :tags
   has_many :subjects
   has_many :educational_stages
diff --git a/db/migrate/20170109133754_add_nickname_to_user.rb b/db/migrate/20170109133754_add_nickname_to_user.rb
new file mode 100644
index 0000000000000000000000000000000000000000..37f4c21bdfc000abe35e91e9893185c58418b155
--- /dev/null
+++ b/db/migrate/20170109133754_add_nickname_to_user.rb
@@ -0,0 +1,5 @@
+class AddNicknameToUser < ActiveRecord::Migration[5.0]
+  def change
+    add_column :users, :nickname, :string
+  end
+end
diff --git a/lib/tasks/attachment_maintaining_service.rake b/lib/tasks/attachment_maintaining_service.rake
new file mode 100644
index 0000000000000000000000000000000000000000..6587edd4c8c5d01ee8f47c379fdbe34b4b06925d
--- /dev/null
+++ b/lib/tasks/attachment_maintaining_service.rake
@@ -0,0 +1,25 @@
+require 'fileutils'
+
+  namespace :attachment_maintaining_service do
+    desc 'Removing 10 attachments'
+    task remove_attachments: :environment do
+      m = sort_directories.first(10)
+      m.each do |mm|
+        #puts (mm)
+        FileUtils.rm_r(mm)
+      end
+    end
+
+    def sort_directories
+      files_sorted_by_time = Dir[dir_path].sort_by{ |f| File.atime(f) }
+      files_sorted_by_time
+    end
+
+    private
+
+    def dir_path
+      c = Rails.root.join('public','attachments','*').to_s
+      c
+    end
+
+  end