my %property_id;
sub property_id {
  my ($db, $property) = @_;
  my $pid;
  unless (defined($pid = $property_id{$property}) {
    ($pid) = $db->query(..., $property)->list;
    unless (defined($pid)) {
      $db->query("INSERT ...", $property);
      $pid = $db->last_insert_id();
    }
    $property_id{$property} = $pid;
  }
  return $pid;
}