Track how many posts a user reads each day in user_visits

db/migrate/20140124202427_add_posts_read_to_user_visits.rb

@@ -0,0 +1,12 @@
+class AddPostsReadToUserVisits < ActiveRecord::Migration
+  def up
+    add_column :user_visits, :posts_read, :integer, default: 0
+
+    # Can't accurately back-fill this column. Assume everyone read at least one post per visit.
+    execute "UPDATE user_visits SET posts_read = 1"
+  end
+
+  def down
+    remove_column :user_visits, :posts_read
+  end
+end