/**
* Make current page a root page, provided that a page
* with the same scope does not exist.
*
* @return PageNode
*/
public function makeRoot()
{
// guard agains root with the same scope
$present = $this->newQuery()->where($this->getScopedConditions())->whereNull($this->getParentColumnName())->count() > 0;
if ($present) {
throw new \Baum\MoveNotPossibleException();
}
return parent::makeRoot();
}