Cache trade info on items#show, finally! I think it's the performance culprit.

app/models/closet_hanger.rb

@@ -51,6 +51,14 @@ class ClosetHanger < ActiveRecord::Base
     }.to_json
   end
 
+  def possibly_null_closet_list
+    list || user.null_closet_list(owned)
+  end
+
+  def trading?
+    possibly_null_closet_list.trading?
+  end
+
   def verb(subject=:someone)
     self.class.verb(subject, owned?)
   end

app/models/closet_list.rb

@@ -1,7 +1,7 @@
 class ClosetList < ActiveRecord::Base
   belongs_to :user
-  has_many :hangers, :class_name => 'ClosetHanger', :foreign_key => 'list_id',
-    :dependent => :nullify
+  has_many :hangers, :class_name => 'ClosetHanger', :foreign_key => 'list_id'
+  # Nullification of associated records occurs in the ClosetListObserver.
 
   attr_accessible :description, :hangers_owned, :name, :visibility
 
@@ -27,5 +27,70 @@ class ClosetList < ActiveRecord::Base
       end
     end
   end
-end
 
+  module VisibilityMethods
+    delegate :trading?, to: :visibility_level
+
+    def visibility_level
+      ClosetVisibility.levels[visibility]
+    end
+
+    def trading_changed?
+      return false unless visibility_changed?
+      level_change = visibility_change.map { |v| ClosetVisibility.levels[v] }
+      old_trading, new_trading = level_change.map(&:trading?)
+      old_trading != new_trading
+    end
+  end
+
+  include VisibilityMethods
+
+  class Null
+    include VisibilityMethods
+    attr_reader :user
+
+    def initialize(user)
+      @user = user
+    end
+
+    def hangers
+      user.closet_hangers.unlisted.where(owned: hangers_owned)
+    end
+  end
+
+  class NullOwned < Null
+    def hangers_owned
+      true
+    end
+
+    def visibility
+      user.owned_closet_hangers_visibility
+    end
+
+    def visibility_changed?
+      user.owned_closet_hangers_visibility_changed?
+    end
+
+    def visibility_change
+      user.owned_closet_hangers_visibility_change
+    end
+  end
+
+  class NullWanted < Null
+    def hangers_owned
+      false
+    end
+
+    def visibility
+      user.wanted_closet_hangers_visibility
+    end
+
+    def visibility_changed?
+      user.wanted_closet_hangers_visibility_changed?
+    end
+
+    def visibility_change
+      user.wanted_closet_hangers_visibility_change
+    end
+  end
+end

app/models/closet_visibility.rb

@@ -16,6 +16,10 @@ module ClosetVisibility
     def human_name
       I18n.translate "closet_hangers.visibility.#{name}.name"
     end
+
+    def trading?
+      id >= LEVELS_BY_NAME[:trading].id
+    end
   end
 
   LEVELS = [

app/models/item_observer.rb

@@ -1,6 +1,4 @@
 class ItemObserver < ActionController::Caching::Sweeper
-  include FragmentExpiration
-  
   def after_create(item)
     Resque.enqueue(Item::CreateTask, item.id)
   end

app/models/user.rb

@@ -85,6 +85,10 @@ class User < ActiveRecord::Base
     end
   end
 
+  def null_closet_list(owned)
+    owned ? ClosetList::NullOwned.new(self) : ClosetList::NullWanted.new(self)
+  end
+
   def self.find_or_create_from_remote_auth_data(user_data)
     user = find_or_initialize_by_remote_id_and_auth_server_id(
       user_data['id'],

app/models/user_sweeper.rb

@@ -1,13 +1,8 @@
 class UserSweeper < ActionController::Caching::Sweeper
   observe User
-  
-  def before_save(user)
-    if user.points_changed?
-      points_to_beat = User.points_required_to_pass_top_contributor(User::PreviewTopContributorsCount - 1)
-      if user.points >= points_to_beat
-        expire_fragment(:controller => 'outfits', :action => 'new', :action_suffix => 'top_contributors')
-      end
-    end
-    true
+  def after_update(user)
+    # Delegate null-list sweeping to the ClosetListObserver.
+    null_lists = [true, false].map { |owned| user.null_closet_list(owned) }
+    null_lists.each { |list| ClosetListObserver.instance.after_update(list) }
   end
 end

app/views/items/show.html.haml

@@ -61,15 +61,17 @@
       - else
         = list_zones @restricted_zones
 
-#trade-hangers
-  - [true, false].each do |owned|
-    %p
-      %strong
-        = trading_closet_hangers_header(owned, @trading_closet_hangers_by_owned[owned].size)
-      = render_trading_closet_hangers(owned)
-      %span.toggle
-        %span.more= t '.trading_closet_hangers.show_more'
-        %span.less= t '.trading_closet_hangers.show_less'
+- localized_cache "items/#{@item.id} trade_hangers" do
+  #trade-hangers
+    - [true, false].each do |owned|
+      - localized_cache "items/#{@item.id} trade_hangers owned=#{owned}" do
+        %p
+          %strong
+            = trading_closet_hangers_header(owned, @trading_closet_hangers_by_owned[owned].size)
+          = render_trading_closet_hangers(owned)
+          %span.toggle
+            %span.more= t '.trading_closet_hangers.show_more'
+            %span.less= t '.trading_closet_hangers.show_less'
 
 - localized_cache 'items#show preview_header' do
   #item-preview-header

config/application.rb

@@ -20,7 +20,9 @@ module OpenneoImpressItems
     # config.plugins = [ :exception_notification, :ssl_requirement, :all ]
 
     # Activate observers that should always be running
-    config.active_record.observers = :contribution_observer, :item_observer, :pet_type_observer, :user_sweeper
+    config.active_record.observers = [:closet_hanger_observer,
+      :closet_list_observer, :contribution_observer, :item_observer,
+      :pet_type_observer, :user_sweeper]
 
     # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
     # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.