discourse/db/migrate/20150617234511_add_staff_index_to_users.rb

class AddStaffIndexToUsers < ActiveRecord::Migration
  def change
    add_index :users, [:id], name: 'idx_users_admin', where: 'admin'
    add_index :users, [:id], name: 'idx_users_moderator', where: 'moderator'
  end
end