/**
* calculate query identifier
*
* @param string|Query $query
* @return string
*/
protected function getResultsID($query)
{
if ($query == '') {
throw new \DomainException("Query ID cannot be empty");
}
$id = 'results';
if ($query instanceof Query) {
$id .= $query->getUrlHash();
} else {
$id .= $query;
}
return $id;
}