construct_id_map

# File activerecord/lib/active_record/association_preload.rb, line 82
      def construct_id_map(records)
        id_to_record_map = {}
        ids = []
        records.each do |record|
          ids << record.id
          mapped_records = (id_to_record_map[record.id.to_s] ||= [])
          mapped_records << record
        end
        ids.uniq!
        return id_to_record_map, ids
      end