code: private function compress($dwnlSnap, $pv, $calcId)
      {
          $in = new \Praxigento\Core\Data();
          $in->set(PPhase1::IN_DWNL_PLAIN, $dwnlSnap);
          $in->set(PPhase1::IN_PV, $pv);
          $in->set(PPhase1::IN_CALC_ID, $calcId);
          $in->set(PPhase1::IN_KEY_CALC_ID, EBonDwnl::A_CALC_REF);
          $in->set(PPhase1::IN_KEY_CUST_ID, QBSnap::A_CUST_ID);
          $in->set(PPhase1::IN_KEY_PARENT_ID, QBSnap::A_PARENT_ID);
          $in->set(PPhase1::IN_KEY_DEPTH, QBSnap::A_DEPTH);
          $in->set(PPhase1::IN_KEY_PATH, QBSnap::A_PATH);
          $in->set(PPhase1::IN_KEY_PV, EBonDwnl::A_PV);
          $out = $this->procPhase1->exec($in);
          $updates = $out->get(PPhase1::OUT_COMPRESSED);
          $pvTransfers = $out->get(PPhase1::OUT_PV_TRANSFERS);
          $result = [$updates, $pvTransfers];
          return $result;
      }
docs: Wrapper for compression sub-process.
  
  @param array $dwnlSnap see \Praxigento\Downline\Repo\Query\Snap\OnDate\Builder
  @param array $pv [custId => pv]
  @param int $calcId
  @return array [$updates, $pvTransfers]