* since that was checked earlier on.
*/
VLSNRange shortenFromEnd(final VLSN deleteStart) {
VLSN newLast = deleteStart.getPrev();
assert newLast.compareTo(lastTxnEnd) >= 0 :
"Can't truncate at " + newLast +
" because it overwrites a commit at " + lastTxnEnd;
if (newLast.equals(NULL_VLSN)) {
return new VLSNRange(NULL_VLSN, NULL_VLSN, NULL_VLSN, NULL_VLSN);