@Override
    public SamzaSqlInputMessage apply(SamzaSqlInputMessage message) {
      message.getMetadata().setIsSystemMessage(relConverter.isSystemMessage(message.getKeyAndMessageKV()));
      return message;
    }
Function that populates whether the message is a system message.
TODO This should ideally be populated by the InputTransformer in future.
samza-sql/src/main/java/org/apache/samza/sql/translator/ScanTranslator.java