/**
* Add a "group by" clause to the query.
*
* @param array|string $column,...
* @return $this
*/
public function groupBy()
{
foreach (func_get_args() as $arg) {
$this->query->group($arg)->ungroup()->map(function ($doc) {
return $doc('reduction')->nth(0);
});
}
return $this;
}
