[HBASE-26742] Comparator of NOT_EQUAL NULL is invalid for checkAndMutate

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.8.0, 3.0.0-alpha-2, 2.4.9
• Fix Version/s: 2.5.0, 3.0.0-alpha-3, 2.4.10

Release Note

The semantics of checkAndPut for null(or empty) value comparator is changed, the old match is always true.
But we should consider that EQUAL or NOT_EQUAL for null check is a common usage, so the semantics of checkAndPut for matching null is correct now.
There is rare use of LESS or GREATER null, so keep the semantics for them.

• Assignee: Xiaolin Ha
• Reporter: Xiaolin Ha
• Created: 08/Feb/22 04:18
• Updated: 17/Feb/22 06:46
• Resolved: 16/Feb/22 03:26

Description

 In server side, checkAndMutate ignores CompareOperator for null or empty comparator value, but NOT_EQUAL should be treated specially.

The check logic in HRegion#checkAndMutateInternal is as follows,

boolean valueIsNull =
  comparator.getValue() == null || comparator.getValue().length == 0;
if (result.isEmpty() && valueIsNull) {
  matches = true;
} else if (result.size() > 0 && result.get(0).getValueLength() == 0 && valueIsNull) {
  matches = true;
  cellTs = result.get(0).getTimestamp();
} else if (result.size() == 1 && !valueIsNull) {
  Cell kv = result.get(0);
  cellTs = kv.getTimestamp();
  int compareResult = PrivateCellUtil.compareValue(kv, comparator);
  matches = matches(op, compareResult);
}

For current logics, here are some  counter examples(Comparator value is set null),

1. result is null, operator is NOT_EQUAL, but matches is true;
2. result size >0, the value of the first cell is empty, operator is NOT_EQUAL, but matches is true;
3. result size is 1, operator is NOT_EQUAL, but matches is false;

Issue Links

• links to: GitHub Pull Request #4105