// Store the properties into a vector
   vec_str_int_type propvec; propvec.reserve(num_keys);

   #pragma omp parallel for schedule(static, 1)
   for (int i = 0; i < nmaps; ++i) {

      // casket.tkh-00000-of-00004
      // casket.tkh-00001-of-00004
      // casket.tkh-00002-of-00004
      // casket.tkh-00003-of-00004

      char path[255];
      std::sprintf(path, "/dev/shm/casket.tkh-%05d-of-%05d", i, nmaps);
      tkrzw::HashDBM dbm; dbm.Open(path, false).OrDie();
      int64_t num_keys = dbm.CountSimple();

      if (num_keys > 0) {
         vec_str_int_type locvec; locvec.reserve(num_keys);

         std::string key, value;
         int64_t *bigendian_num = reinterpret_cast<int64_t*>(value.data());
         std::unique_ptr<tkrzw::DBM::Iterator> iter = dbm.MakeIterator();

         iter->First();
         while (iter->Get(&key, &value) == tkrzw::Status::SUCCESS) {
            locvec.emplace_back(key, bswap_64(*bigendian_num));
            iter->Next();
         }

         #pragma omp critical
         propvec.insert(
            // Append local vector to propvec
            propvec.end(),
            std::make_move_iterator(locvec.begin()),
            std::make_move_iterator(locvec.end())
         );
      }

      dbm.Close();
   }