@Override
  public boolean isTxnValid(long txnid) {
    if (txnid > highWatermark) {
      return false;
    }
    return Arrays.binarySearch(exceptions, txnid) < 0;
  }
Used if there are no open transactions in the snapshot
storage-api/src/java/org/apache/hadoop/hive/common/ValidReadTxnList.java