Delete award emoji when deleting a user

CHANGELOG

@@ -8,6 +8,7 @@ v 8.10.0 (unreleased)
   - Refactor repository paths handling to allow multiple git mount points
   - Optimize system note visibility checking by memoizing the visible reference count !5070
   - Add Application Setting to configure default Repository Path for new projects
+  - Delete award emoji when deleting a user
   - Remove pinTo from Flash and make inline flash messages look nicer !4854 (winniehell)
   - Wrap code blocks on Activies and Todos page. !4783 (winniehell)
   - Align flash messages with left side of page content !4959 (winniehell)

app/models/user.rb

@@ -87,7 +87,7 @@ class User < ActiveRecord::Base
   has_many :builds,                   dependent: :nullify, class_name: 'Ci::Build'
   has_many :todos,                    dependent: :destroy
   has_many :notification_settings,    dependent: :destroy
-  has_many :award_emoji,              as: :awardable, dependent: :destroy
+  has_many :award_emoji,              dependent: :destroy
 
   #
   # Validations

db/migrate/20160712171823_remove_award_emojis_with_no_user.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class RemoveAwardEmojisWithNoUser < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # When using the methods "add_concurrent_index" or "add_column_with_default"
+  # you must disable the use of transactions as these methods can not run in an
+  # existing transaction. When using "add_concurrent_index" make sure that this
+  # method is the _only_ method called in the migration, any other changes
+  # should go in a separate migration. This ensures that upon failure _only_ the
+  # index creation fails and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  # disable_ddl_transaction!
+
+  def up
+    AwardEmoji.joins('LEFT JOIN users ON users.id = user_id').where('users.id IS NULL').destroy_all
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160707104333) do
+ActiveRecord::Schema.define(version: 20160712171823) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"