public function getRpPoints($rp, $metric, $tags, $granularity, $startDt = null, $endDt = null, $timezone = 'utc') {
        
        if (null == $rp || null == $metric) {
            return [];
        }
        
        $where = [];
        
        $query = $this->db->getQueryBuilder()
                ->retentionPolicy($rp)
                ->sum('value')
                ->from($metric);

        if (isset($endDt)) {
            $where[] = "time <= '" . $endDt . "'";
        }
        
        if (isset($startDt)) {
            $where[] = "time >= '" . $startDt . "'";
        }
        
        foreach ($tags as $key => $val) {
            $where[] = "$key = '" . $val . "'";
        }

        $query->where($where);
        
        $groupBy = "time(1d) tz('" . $timezone . "')";
        if ($granularity == self::GRANULARITY_HOURLY) {
            //timeoffset doesn't work hourly
            $groupBy = "time(1h) tz('" . $timezone . "')";
        } else if ($granularity == self::GRANULARITY_DAILY) {
            $groupBy = "time(1d) tz('" . $timezone . "')";
        } else if ($granularity == self::GRANULARITY_WEEKLY) {
            $groupBy = "time(1w) tz('" . $timezone . "')";
        }
        $query->groupBy($groupBy);

        return $query->getResultSet()->getPoints();
    }