Sort on and index taggings, ftw

app/controllers/tags_controller.rb

@@ -59,12 +59,12 @@ class TagsController < ApplicationController
     @tag = ActsAsTaggableOn::Tag.where(:name => params[:name]).first
     if @tag
       @posts = @posts.joins("LEFT OUTER JOIN comments ON comments.post_id = posts.id").
-                      joins("INNER JOIN taggings ON (taggings.tag_id = #{@tag.id} AND 
+                      joins("INNER JOIN taggings ON (taggings.tag_id = #{@tag.id} AND
                              ((taggable_id = posts.id AND taggable_type = 'Post') OR (taggings.taggable_type = 'Comment' AND taggings.taggable_id = comments.id)))")
 
       max_time = params[:max_time] ? Time.at(params[:max_time].to_i) : Time.now
       @posts = @posts.where(StatusMessage.arel_table[:created_at].lt(max_time))
-      @posts = @posts.includes({:comments => {:author => :profile}}, :photos).order('posts.created_at DESC').limit(15)
+      @posts = @posts.includes({:comments => {:author => :profile}}, :photos).order('taggings.created_at DESC').limit(15)
     else
       @posts = []
     end

db/migrate/20110707221112_index_taggings_created_at.rb

@@ -0,0 +1,8 @@
+class IndexTaggingsCreatedAt < ActiveRecord::Migration
+  def self.up
+    add_index :taggings, :created_at
+  end
+
+  def self.down
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20110705003445) do
+ActiveRecord::Schema.define(:version => 20110707221112) do
 
   create_table "aspect_memberships", :force => true do |t|
     t.integer  "aspect_id",  :null => false
@@ -343,6 +343,7 @@ ActiveRecord::Schema.define(:version => 20110705003445) do
     t.datetime "created_at"
   end
 
+  add_index "taggings", ["created_at"], :name => "index_taggings_on_created_at"
   add_index "taggings", ["tag_id"], :name => "index_taggings_on_tag_id"
   add_index "taggings", ["taggable_id", "taggable_type", "context"], :name => "index_taggings_on_taggable_id_and_taggable_type_and_context"
   add_index "taggings", ["taggable_id", "taggable_type", "tag_id"], :name => "index_taggings_uniquely", :unique => true