associated_records_by_owner

# File activerecord/lib/active_record/associations/preloader/through_association.rb, line 13
        def associated_records_by_owner(preloader)
          preloader.preload(owners,
                            through_reflection.name,
                            through_scope)

          through_records = owners.map do |owner|
            association = owner.association through_reflection.name

            [owner, Array(association.reader)]
          end

          reset_association owners, through_reflection.name

          middle_records = through_records.map { |(_,rec)| rec }.flatten

          preloaders = preloader.preload(middle_records,
                                         source_reflection.name,
                                         reflection_scope)

          @preloaded_records = preloaders.flat_map(&:preloaded_records)

          middle_to_pl = preloaders.each_with_object({}) do |pl,h|
            pl.owners.each { |middle|
              h[middle] = pl
            }
          end

          record_offset = {}
          @preloaded_records.each_with_index do |record,i|
            record_offset[record] = i
          end

          through_records.each_with_object({}) { |(lhs,center),records_by_owner|
            pl_to_middle = center.group_by { |record| middle_to_pl[record] }

            records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles|
              rhs_records = middles.flat_map { |r|
                association = r.association source_reflection.name

                association.reader
              }.compact

              rhs_records.sort_by { |rhs| record_offset[rhs] }
            end
          }
        end