performance improvement by eager loading stuff

app/controllers/topics_controller.rb

@@ -8,8 +8,8 @@ class TopicsController < ApplicationController
   # GET /topics
   # GET /topics.xml
   def index
-    # TODO Here be unoptimized code.
-    @topics = Topic.find(:all).sort {|a,b| b.posts.last.created_at <=> a.posts.last.created_at }
+    @topics = Topic.find(:all, :include => [:tags, :posts])
+    @topics.sort! {|a,b| b.posts.last.created_at <=> a.posts.last.created_at }
     @tags = Topic.tag_counts.sort {|a,b| b.count <=> a.count }[0..19]
 
     respond_to do |format|

app/models/topic.rb

@@ -1,14 +1,9 @@
 class Topic < ActiveRecord::Base
   acts_as_taggable
 
-  has_many   :posts
+  has_many   :posts, :include => :user, :dependent => :destroy
   has_many   :posters, :through => :posts, :source => :user
 
-  has_one    :starter, :class_name => 'User', :through => :posts, :source => :user,
-                       :order => '"posts".created_at ASC'
-  has_one    :latestr, :class_name => "User", :through => :posts, :source => :user,
-                       :order => '"posts".created_at DESC'
-
   has_many   :viewings
   has_many   :viewers, :through => :views, :source => :user
 
@@ -24,7 +19,7 @@ def read_by(user)
     v.seen = Time.now
     v.save
   end
-
+  
   private
     def sanitize_fields
       self.title = helpers.sanitize(title)

app/views/topics/_list.html.haml

@@ -5,7 +5,7 @@
       %li.tags
         = "Tags: "         + tags_for_topic(topic.tags)
       /%li.start
-      /  = "Started by: "   + link_to(topic.starter.name, topic.starter)
+      /  = "Started by: "   + link_to(topic.posts.first.name, topic.posts.first)
       %li.last
-        = "Last post by: " + link_to(topic.latestr.name,  topic.latestr)
+        = "Last post by: " + link_to(topic.posts.last.user.name,  topic.posts.last.user)
         = " at "           + link_to(topic.posts.last.created_at.to_formatted_s(:short), topic_post_path(topic, topic.posts.last))