Add image fingerprints to users

db/migrate/20120219161649_add_user_image_fingerprint.rb

@@ -0,0 +1,16 @@
+class AddUserImageFingerprint < ActiveRecord::Migration
+  def up
+    add_column :users, :image_fingerprint, :string, :null => true
+
+    User.where("image_file_name IS NOT NULL").find_each do |user|
+      image = user.image
+
+      user.image_fingerprint = image.generate_fingerprint(image)
+      user.save!
+    end
+  end
+
+  def down
+    remove_column :users, :image_fingerprint
+  end
+end