404 page had horrible perf, it was using "take" instead of limit.

in such cases EVERY row is materialized and only after the limit is applied.

So ... imagine what happens on a forum with 2,000,000 topics

app/controllers/exceptions_controller.rb

@@ -1,5 +1,5 @@
 class ExceptionsController < ApplicationController
-  skip_before_filter :check_xhr
+  skip_before_filter :check_xhr, :preload_json
 
   def not_found
     # centralize all rendering of 404 into app controller

lib/topic_query.rb

@@ -65,12 +65,12 @@ class TopicQuery
       "CASE WHEN (topics.pinned_at IS NOT NULL) THEN 0 ELSE 1 END, topics.bumped_at DESC"
     end
 
-    def top_viewed(max)
-      Topic.listable_topics.visible.secured.order('views desc').take(10)
+    def top_viewed(max = 10)
+      Topic.listable_topics.visible.secured.order('views desc').limit(max)
     end
 
-    def recent(max)
-      Topic.listable_topics.visible.secured.order('created_at desc').take(10)
+    def recent(max = 10)
+      Topic.listable_topics.visible.secured.order('created_at desc').limit(max)
     end
   end