Checking in the migration helps.

db/migrate/20110213052742_add_more_indicies.rb

@@ -0,0 +1,14 @@
+class AddMoreIndicies < ActiveRecord::Migration
+  def self.up
+    #For making validates_uniqueness_of, :case_sensitive => false, fast
+    add_index :users, [:id, :username], :unique => true
+    add_index :users, [:id, :email], :unique => true
+    add_index :people, [:id, :diaspora_handle], :unique => true
+
+    #For the includes of photos in the stream
+    add_index :posts, [:id, :type]
+  end
+
+  def self.down
+  end
+end