DataMapper - Counting related items

[eluser]NeilyM[/eluser]
Hi guys

I have a question about counting related items when using Datamapper. The following hopefully illustrates what I'm trying to do because my own code would be pretty meaningless without the context. This example has the same "has_many" and "has_one" releationships as mine.

Country has_many Person
Continent has_many Country
Country has_one Continent

I have a Continent and I need to know how many people are in it.

$continent = new Continent;
$continent->get_by_id(1);
$count = $continent->where_related('country/person')->count();

... is what I think I need but it doesn't seem to work.

$continent = new Continent;
$continent->get_by_id(1);
$count = $continent->where_related('country/person')->get()->count();

...does seem to work but I think I am right in saying it loads all the Person records and is therefore not an ideal solution.

Any ideas anyone?

Thank you once again.

Cheers,

NeilyM