ids_writer

# File activerecord/lib/active_record/associations/collection_association.rb, line 60
      def ids_writer(ids)
        primary_key = reflection.association_primary_key
        pk_type = klass.type_for_attribute(primary_key)
        ids = Array(ids).compact_blank
        ids.map! { |id| pk_type.cast(id) }

        records = if klass.composite_primary_key?
          klass.where(primary_key => ids).index_by do |record|
            primary_key.map { |primary_key| record._read_attribute(primary_key) }
          end
        else
          klass.where(primary_key => ids).index_by do |record|
            record._read_attribute(primary_key)
          end
        end.values_at(*ids).compact

        if records.size != ids.size
          found_ids = records.map { |record| record._read_attribute(primary_key) }
          not_found_ids = ids - found_ids
          klass.all.raise_record_not_found_exception!(ids, records.size, ids.size, primary_key, not_found_ids)
        else
          replace(records)
        end
      end