@Override public Object getMessageKey(SamzaSqlRelMessage message) { SamzaSqlRelRecord keyRecord = getMessageKeyRelRecord(message); // If all the message key rel record values are null, return null message key. if (keyRecord.getFieldValues().stream().allMatch(Objects::isNull)) { return null; } // Using the table key converter, convert message key from rel format to the record key format. return relTableKeyConverter.convertToTableKeyFormat(keyRecord); }