[jira] [Created] (CASSANDRA-15640) digest may not match when single partition named queries skip older sstables

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

ZhaoYang created CASSANDRA-15640:
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             Summary: digest may not match when single partition named queries skip older sstables
                 Key: CASSANDRA-15640
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15640
             Project: Cassandra
          Issue Type: Bug
          Components: Legacy/Local Write-Read Paths
            Reporter: ZhaoYang


Name queries (aka. single partition query with full clustering keys) query sstables sequentially in recency order, in the hope that most recent sstables will contain most recent data, so that they can avoid reading older sstables in {{SinglePartitionReadCommand#reduceFilter}}.

Unfortunately, this optimization may cause digest mismatch if older sstables contain range tombstone or row deletion with lower timestamp. [Test Code|https://github.com/jasonstack/cassandra/commit/3dfa29bb34bc237ab2b68f849906c09569c5cc94]
{code:java}
Table with (pk, ck1, ck2)

Node1:
* delete row (pk=1, ck1=1) with ts=10
* insert row (pk=1, ck1=1, ck2=1) with ts=11

Node2:
* delete row (pk=1, ck1=1) with ts=10
* flush into sstable1
* insert row (pk=1, ck1=1, ck2=1) with ts=11
* flush into sstable2

Query with pk=1 and ck1=1 and ck2=1
* node1 returns: RT open marker, row, RT close marker
* node2 returns: row  (because sstable1 is skipped)

Note: similar mismatch can happen with row deletion as well.
{code}
In the above example: Is it safe to ignore RT or row deletion if row liveness has higher timestamp for named queries in node1?



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