public static PlanFragment deserialize(ByteBuffer byteBuffer) {
    PlanFragmentId planFragmentId = PlanFragmentId.deserialize(byteBuffer);
    byte hasTypeProvider = ReadWriteIOUtils.readByte(byteBuffer);
    TypeProvider typeProvider = null;
    if (hasTypeProvider == 1) {
      typeProvider = TypeProvider.deserialize(byteBuffer);
    }
    PlanFragment planFragment =
        new PlanFragment(planFragmentId, deserializeHelper(byteBuffer, typeProvider));
    planFragment.setTypeProvider(typeProvider);
    return planFragment;
  }
PlanFragment contains a sub-query of distributed query.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/PlanFragment.java