an alternate (more aggressive) approach to making to_yaml work

to_yaml.rb

module ActiveRecord
  class Base
    def to_yaml_with_association_pruning(opts = {})
      # detect and remove any cached associations
      self.class.reflect_on_all_associations.each do |a|
        ivar = "@#{a.name}"
        remove_instance_variable(ivar) if instance_variable_defined?(ivar)
      end
      to_yaml_without_association_pruning(opts)
    end
    alias_method_chain :to_yaml, :association_pruning
  end
end