[jira] [Created] (CASSANALYTICS-180) TokenPartitioner fails to detect range gap in reader

["Yifan Cai (Jira)" <ji...@apache.org>]

Yifan Cai created CASSANALYTICS-180:
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             Summary: TokenPartitioner fails to detect range gap in reader
                 Key: CASSANALYTICS-180
                 URL: https://issues.apache.org/jira/browse/CASSANALYTICS-180
             Project: Apache Cassandra Analytics
          Issue Type: Bug
          Components: Reader
            Reporter: Yifan Cai


Found the minor bug when inspecting the code. The implementation filters out the non-empty ranges wrongly when detecting gaps in the range split. 
Below is the test to prove the bug.
It is a minor bug because no correctness is affected; the range split step is mathematically gap-free today. 
It is still worth fixing because the check itself is broken and won't catch any future regression that reintroduces a coverage gap.

 

 
{code:java}
@Test
public void testValidateCompleteRangeCoverageFailsToDetectGap()
{
    Partitioner partitioner = Partitioner.Murmur3Partitioner;
    List<Range<BigInteger>> subRangesWithGap = Arrays.asList(
    Range.openClosed(partitioner.minToken(), partitioner.minToken().add(BigInteger.ONE)),
    Range.openClosed(partitioner.minToken().add(BigInteger.ONE).add(BigInteger.TEN), partitioner.maxToken()));
    // leaves (minToken()+1, minToken()+11] uncovered -- a real, non-empty gap
    RangeSet<BigInteger> missingRangeSet = TreeRangeSet.create();
    missingRangeSet.add(Range.closed(partitioner.minToken(), partitioner.maxToken()));
    subRangesWithGap.forEach(missingRangeSet::remove);
    // This mirrors TokenPartitioner#validateCompleteRangeCoverage exactly
    List<Range<BigInteger>> missingRanges = missingRangeSet.asRanges().stream()
                                                           .filter(Range::isEmpty)
                                                           .collect(Collectors.toList());
    // BUG: missingRanges is empty here even though a real gap exists,
    // because the filter keeps only degenerate zero-width ranges instead of dropping them.
    assertThat(missingRanges).isEmpty(); // passes -- but it should have caught the gap and failed 
}
{code}
 



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