global class AggregateResultIterator implements Iterator<AggregateResult> {
  AggregateResult [] results {get;set;}
  // tracks which result item is returned
  Integer index {get; set;}

  global AggregateResultIterator(String query) {
    index = 0;
    results = Database.query(query);
  }

  global boolean hasNext(){
    return results != null && !results.isEmpty() && index < results.size();
  }

  global AggregateResult next(){
    return results[index++];
  }
}