Part of DBIx::Class::Storage::DBI->insert()

gistfile1.pl

  # list of primary keys we try to fetch from the database
  # both not-exsists and scalarrefs are considered
  my %fetch_pks;
  for ($source->primary_columns) {
    $fetch_pks{$_} = scalar keys %fetch_pks  # so we can preserve order for prettyness
      if ! exists $to_insert->{$_} or ref $to_insert->{$_} eq 'SCALAR';
  }

  my ($sqla_opts, @ir_container);
  if ($self->_use_insert_returning) {

    # retain order as declared in the resultsource
    for (sort { $fetch_pks{$a} <=> $fetch_pks{$b} } keys %fetch_pks ) {
      push @{$sqla_opts->{returning}}, $_;
      $sqla_opts->{returning_container} = \@ir_container
        if $self->_use_insert_returning_bound;
    }
  }