[CASSANDRA-18013] Splitter sometimes creates different number of splits than requested

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.11.15, 4.0.8, 4.1-rc1, 4.1, 5.0-alpha1, 5.0
• Component/s: Local/Compaction
• Bug Category: Correctness - Consistency
• Severity: Normal
• Complexity: Normal
• Discovered By: Adhoc Test
• Platform: All
• Since Version: 3.2

Source Control Link

https://github.com/apache/cassandra/commit/9213335f59293926b2d643fa8a156a882495dd42

Test and Documentation Plan

run regressions

• Assignee: Jacek Lewandowski
• Reporter: Jacek Lewandowski

Authors

Jacek Lewandowski

Reviewers

Marcus Eriksson

• Created: 03/Nov/22 15:41
• Updated: 12/Sep/23 13:03
• Resolved: 09/Nov/22 16:29

Description

Splitter in some cases may produce one split more than requested. When it happens, it fails with assertion error when assertions are enabled.

Test to reproduce the issue:

        Splitter splitter = getSplitter(Murmur3Partitioner.instance);
        long lt = 0;
        long rt = 31;
        Range<Token> range = new Range<>(getWrappedToken(Murmur3Partitioner.instance, BigInteger.valueOf(lt)),
                                         getWrappedToken(Murmur3Partitioner.instance, BigInteger.valueOf(rt)));

        for (int i = 1; i <= (rt - lt); i++)
        {
            List<Token> splits = splitter.splitOwnedRanges(i, Arrays.asList(new Splitter.WeightedRange(1.0d, range)), false);
            logger.info("{} splits of {} are: {}", i, range, splits);
            Assertions.assertThat(splits).hasSize(i);
        }