.findQuery().get('length') giving result as 0 every time.

.findQuery().get('length') giving result as 0 every time.

I am using .findQuery().get('length') to get total count of records
available in model for specific filtration.
But every time it is showing result as 0.
I have listed my code here.
total:function(){
return App.Person.query({ contacttype: 1 }).get('length');
}.property('@each.isLoaded')