def ReadHuntClientResourcesStats(self, hunt_id, cursor=None):
    """Read/calculate hunt client resources stats."""
    hunt_id_int = db_utils.HuntIDToInt(hunt_id)

    query = """
      SELECT
        COUNT(*),
        SUM(user_cpu_time_used_micros),
        SUM((user_cpu_time_used_micros) * (user_cpu_time_used_micros)),
        SUM(system_cpu_time_used_micros),
        SUM((system_cpu_time_used_micros) * (system_cpu_time_used_micros)),
        SUM(network_bytes_sent),
        SUM(network_bytes_sent * network_bytes_sent),
    """

    scaled_bins = [
        int(1000000 * b) for b in rdf_stats.ClientResourcesStats.CPU_STATS_BINS
    ]

    query += self._BinsToQuery(scaled_bins, "(user_cpu_time_used_micros)")
    query += ","
    query += self._BinsToQuery(scaled_bins, "(system_cpu_time_used_micros)")
    query += ","
    query += self._BinsToQuery(
        rdf_stats.ClientResourcesStats.NETWORK_STATS_BINS, "network_bytes_sent")

    query += " FROM flows "
    query += "FORCE INDEX(flows_by_hunt) "
    query += "WHERE parent_hunt_id = %s AND parent_flow_id IS NULL"

    cursor.execute(query, [hunt_id_int])

    response = cursor.fetchone()
    (count, user_sum, user_sq_sum, system_sum, system_sq_sum, network_sum,
     network_sq_sum) = response[:7]

    stats = rdf_stats.ClientResourcesStats(
        user_cpu_stats=rdf_stats.RunningStats(
            num=count,
            sum=db_utils.MicrosToSeconds(int(user_sum or 0)),
            sum_sq=int(user_sq_sum or 0) / 1e12,
        ),
        system_cpu_stats=rdf_stats.RunningStats(
            num=count,
            sum=db_utils.MicrosToSeconds(int(system_sum or 0)),
            sum_sq=int(system_sq_sum or 0) / 1e12,
        ),
        network_bytes_sent_stats=rdf_stats.RunningStats(
            num=count,
            sum=float(network_sum or 0),
            sum_sq=float(network_sq_sum or 0),
        ),
    )

    offset = 7
    stats.user_cpu_stats.histogram = rdf_stats.StatsHistogram()
    for b_num, b_max_value in zip(
        response[offset:], rdf_stats.ClientResourcesStats.CPU_STATS_BINS):
      stats.user_cpu_stats.histogram.bins.append(
          rdf_stats.StatsHistogramBin(range_max_value=b_max_value, num=b_num))

    offset += len(rdf_stats.ClientResourcesStats.CPU_STATS_BINS)
    stats.system_cpu_stats.histogram = rdf_stats.StatsHistogram()
    for b_num, b_max_value in zip(
        response[offset:], rdf_stats.ClientResourcesStats.CPU_STATS_BINS):
      stats.system_cpu_stats.histogram.bins.append(
          rdf_stats.StatsHistogramBin(range_max_value=b_max_value, num=b_num))

    offset += len(rdf_stats.ClientResourcesStats.CPU_STATS_BINS)
    stats.network_bytes_sent_stats.histogram = rdf_stats.StatsHistogram()
    for b_num, b_max_value in zip(
        response[offset:], rdf_stats.ClientResourcesStats.NETWORK_STATS_BINS):
      stats.network_bytes_sent_stats.histogram.bins.append(
          rdf_stats.StatsHistogramBin(range_max_value=b_max_value, num=b_num))

    query = """
      SELECT
        client_id, flow_id, user_cpu_time_used_micros,
        system_cpu_time_used_micros, network_bytes_sent
      FROM flows
      FORCE INDEX(flows_by_hunt)
      WHERE parent_hunt_id = %s AND parent_flow_id IS NULL AND
            (user_cpu_time_used_micros > 0 OR
             system_cpu_time_used_micros > 0 OR
             network_bytes_sent > 0)
      ORDER BY (user_cpu_time_used_micros + system_cpu_time_used_micros) DESC
      LIMIT 10
    """

    cursor.execute(query, [hunt_id_int])

    for cid, fid, ucpu, scpu, nbs in cursor.fetchall():
      client_id = db_utils.IntToClientID(cid)
      flow_id = db_utils.IntToFlowID(fid)
      stats.worst_performers.append(
          rdf_client_stats.ClientResources(
              client_id=client_id,
              session_id=rdfvalue.RDFURN(client_id).Add(flow_id),
              cpu_usage=rdf_client_stats.CpuSeconds(
                  user_cpu_time=db_utils.MicrosToSeconds(ucpu),
                  system_cpu_time=db_utils.MicrosToSeconds(scpu),
              ),
              network_bytes_sent=nbs))

    return stats