gistfile1.txt

DB[:compute_nodes].
  select_group(:compute_nodes__host).
  join(:aggregate_hosts, host: :host).
  where(aggregate_hosts__deleted_at: nil, compute_nodes__deleted_at: nil).
  select_append{sum(:running_vms).as(:running_vms_sum)}.
  select_append{sum(:vcpus_used).as(:vcpus_used_sum)}.
  select_append{sum(:memory_mb_used).as(:memory_mb_used_sum)}