private function getResultIndices()
{
$indices = array();
if (count($this->params->getIdSites()) > 1 || $this->forceIndexedBySite) {
$indices['site'] = 'idSite';
}
if (count($this->params->getPeriods()) > 1 || $this->forceIndexedByDate) {
$indices['period'] = 'date';
}
return $indices;
}