@Override
  public TSet readSetBegin() throws TException {
    stackLevel++;
    set = new TSet(ORDERED_TYPE, readI32());
    if (set.size == 0 && lastPrimitiveWasNull()) {
      return null;
    }
    return set;
  }
This method always return the same instance of TSet to avoid creating new
instances. It is the responsibility of the caller to read the value before
calling this method again.
serde/src/java/org/apache/hadoop/hive/serde2/thrift/TBinarySortableProtocol.java