Merge branch 'atomaka/feature/link-counter-cache' into 'master'

Add counter cache for links

It is difficult to find out which cards are missing links.  This allows us to easily find those cards.

See merge request !18

app/models/card.rb

@@ -12,7 +12,7 @@ class Card < ActiveRecord::Base
   belongs_to :awaken_type
   belongs_to :dokkan_card, class_name: 'Card', foreign_key: :dokkan_id
 
-  has_and_belongs_to_many :links
+  has_and_belongs_to_many :links, counter_cache: true
 
   has_many :evidences
 

db/migrate/20151103193404_add_links_counter_cache_to_cards.rb

@@ -0,0 +1,14 @@
+class AddLinksCounterCacheToCards < ActiveRecord::Migration
+  def up
+    add_column :cards, :links_count, :integer, default: 0, null: false
+
+    Card.reset_column_information
+    Card.find_each do |card|
+      card.update_attribute(:links_count, card.links.count)
+    end
+  end
+
+  def down
+    remove_column :cards, :links_count
+  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: 20151020212132) do
+ActiveRecord::Schema.define(version: 20151103193404) do
 
   create_table "awaken_types", force: :cascade do |t|
     t.string   "name"
@@ -36,6 +36,7 @@ ActiveRecord::Schema.define(version: 20151020212132) do
     t.integer  "hp_stat_id"
     t.integer  "atk_stat_id"
     t.integer  "def_stat_id"
+    t.integer  "links_count",      default: 0,         null: false
   end
 
   add_index "cards", ["awaken_type_id"], name: "index_cards_on_awaken_type_id"