# File ar-extensions/lib/ar-extensions/synchronize.rb, line 11
    def self.synchronize(instances, key=self.primary_key)
      return if instances.empty?
      
      keys = instances.map(&"#{key}".to_sym)
      klass = instances.first.class
      fresh_instances = klass.find( :all, :conditions=>{ key=>keys }, :order=>"#{key} ASC" )

      instances.each_with_index do |instance, index|
        instance.clear_aggregation_cache
        instance.clear_association_cache
        instance.instance_variable_set '@attributes', fresh_instances[index].attributes
      end
    end