why not first query objects? / #2058

Although the SQL-statement is excellent and probably extremely fast, just meant to use getEfforts for getting the effort-objects and then sum up the values:

e.g.:

Effort::getEffortSum(&$args) 
{
  $sum=0;
  if($efforts= Effort::getEfforts(&$args))) {
    foreach($efforts as $e) {
      $sum+= strToGMTime($e->time_end) - strToGMTime($e->time_start);
    }
  }
  return $sum;
}

echo "sum=" + Effort::getEffortsSum(array('project')=> $project->id));

Or would this method be too slow?