recursive_update fails

Question

Now I can call recursive_update but it still fails and I am not able to find out why.

I got this error:

DBIx::Class::Storage::DBI::_dbh_execute(): DBI Exception: DBD::mysql::st execute failed: Unknown column 'me.key' in 'where clause'

But I don't know why. I want to update a related database, the relationship is defined in the Result and retrieving Data works. But when I try recursive_update the key is unknown? even if I explicite use it:

my $result = $rs->find_or_create({
a_id => xxx, 
# ... other data ....
users => [{ u_id => xxx,}, { u_id => xxx}]
});
$rs->recursive_update($data,
   {
            fixed_fields => [ 'a_id' ],
   }
);

I tried several ways to get the right key (a_id), but I got always the same error message about the "unknown key".

Do I need some special relationship?