order by id instead of created_at

id is indexed while created_at is not

app/controllers/blogposts_controller.rb

@@ -4,7 +4,7 @@ class BlogpostsController < ApplicationController
   before_filter :auth, except: [:index, :show]
 
   def index
-    @posts = Blogpost.order("created_at desc").page(params[:page]).per(10)
+    @posts = Blogpost.order(id: :desc).page(params[:page]).per(10)
   end
 
   def show

app/controllers/forumthreads_controller.rb

@@ -12,9 +12,9 @@ class ForumthreadsController < ApplicationController
   end
   def show
     if params[:reverse] == "true"
-      @replies = @thread.replies.order(created_at: :desc).page(params[:page])
+      @replies = @thread.replies.order(id: :desc).page(params[:page])
     else
-      @replies = @thread.replies.order(:created_at).page(params[:page])
+      @replies = @thread.replies.order(:id).page(params[:page])
     end
   end
 

app/models/forumthread.rb

@@ -106,7 +106,7 @@ class Forumthread < ActiveRecord::Base
     if order_phrase.present?
       threads = threads.order("GREATEST(relevance, reply_rel) DESC")
     else
-      threads = threads.order("sticky desc", "threadreplies.created_at DESC", "forumthreads.created_at DESC")
+      threads = threads.order("sticky DESC", "threadreplies.id DESC", "forumthreads.id DESC")
     end
     threads
   end

app/views/forums/index.html.erb

@@ -18,7 +18,7 @@
               <%= link_to f.name, f, id: "forum-#{f.id}"%>
               <div class="item-info">
                 <% if last_thread = f.threads.last %>
-                  <% last_reply = Threadreply.where(forumthread: f.threads).order(:created_at).last %>
+                  <% last_reply = Threadreply.where(forumthread: f.threads).order(:id).last %>
                   <% if last_reply && last_reply.created_at > last_thread.created_at %>
                     <% if last_reply.thread.can_read?(current_user) %>
                       <%= last_reply.author.name %>