[Dbix-class] postgresql and serial primary key

[Luca Ferrari]

Hi all,
I'm a problem with PostgreSQL serial field used as keys, and it seems
there's something in DBIx I'm not understanding.
My Result has a definition for the column as follows:

__PACKAGE__->add_columns(
  "pk",
  {
    data_type         => "integer",
    is_auto_increment => 1,
    is_nullable       => 0,
    sequence          => "tickets_pk_seq",
  }, ...


when I want to add a new field I do the following (in a catalyst
application) in the controller;

my $current_ticket = $c->model( 'DB::Ticket' )->find_or_new( { pk => $pk } );
...
$current_ticket->update_or_insert();

the problem is that for a new record the pk field is still null, and
therefore the sequence is not called since the value NULL is placed in
the query.
Moreover, since my Result has has_many objects, the null value is
propagated to the child objects.
Is there a way to auto-query the sequence when the record is going to
be inserted? I don't want to query it always to avoid sequence-holes.
Similarly, I don't want to find_or_create records since the user could
not end inserting it and I would have "blank" tuples.
Suggestions?

Thanks,
Luca