N1QL pivot data

SQL++
2 
   SELECT d.dt, (OBJECT TO_STR(v.hr):v.cnt FOR v IN arr END).*
    FROM (SELECT COUNT(1) AS cnt, dt, hr
                 FROM orderV1
                 LET dt = MILLIS_TO_STR(received_date_time,"1111-11-11"),
                          hr = DATE_PART_MILLIS(received_date_time, "hour")
                WHERE dt BETWEEN "2021-03-28" AND "2021-03-29"
                GROUP BY dt, hr) AS d
    GROUP BY d.dt
    LETTING arr = ARRAY_AGG({d.hr, d.cnt});

If you need to generate 0 for missing date checkout Analytics N1QL Query: GROUP BY `dates` base on the given date values