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;
    }