preload_has_many_association

# File activerecord/lib/active_record/association_preload.rb, line 241
      def preload_has_many_association(records, reflection, preload_options={})
        return if records.first.send(reflection.name).loaded?
        options = reflection.options

        primary_key_name = reflection.through_reflection_primary_key_name
        id_to_record_map, ids = construct_id_map(records, primary_key_name || reflection.options[:primary_key])
        records.each {|record| record.send(reflection.name).loaded}

        if options[:through]
          through_records = preload_through_records(records, reflection, options[:through])
          through_reflection = reflections[options[:through]]
          unless through_records.empty?
            source = reflection.source_reflection.name
            through_records.first.class.preload_associations(through_records, source, options)
            through_records.each do |through_record|
              through_record_id = through_record[reflection.through_reflection_primary_key].to_s
              add_preloaded_records_to_collection(id_to_record_map[through_record_id], reflection.name, through_record.send(source))
            end
          end

        else
          set_association_collection_records(id_to_record_map, reflection.name, find_associated_records(ids, reflection, preload_options),
                                             reflection.primary_key_name)
        end
      end