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https://issues.apache.org/jira/browse/CASSANDRA-21356?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arjun Ashok reassigned CASSANDRA-21356:
---------------------------------------
Assignee: Arjun Ashok
> CursorBasedCompaction: ReusableLivenessInfo.isExpiring() incorrectly returns
> true for tombstone cells, corrupting cursor-compacted SSTable format and cell
> reconciliation
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-21356
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21356
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Local/Compaction, Local/SSTable
> Reporter: Arjun Ashok
> Assignee: Arjun Ashok
> Priority: Normal
>
> When the cursor compaction path encounters a tombstone cell (a column deleted
> via INSERT ... null or DELETE), it incorrectly sets IS_EXPIRING_MASK in
> addition to IS_DELETED_MASK. This causes an extra TTL delta byte to be
> written to Data.db for every tombstone cell. Any SSTable reader relying on
> the format invariant that IS_DELETED_MASK and IS_EXPIRING_MASK are mutually
> exclusive will misalign on all bytes following a tombstone cell in a
> cursor-compacted SSTable.
>
>
>
> The same root cause also corrupts cell reconciliation during merge. When two
> SSTables hold the same column at the same timestamp (one as a tombstone, one
> as an expiring cell) `resolveRegular()` uses `!isExpiring()` to identify
> tombstones, which also returned false for tombstone cells due to the same
> bug. Both cells appeared identical to the tie-breaking logic, which then fell
> through to comparing localExpirationTime values. Since an expiring cell's
> localExpirationTime is a future timestamp and a tombstone's is a past
> deletion timestamp, the expiring cell always won, resurrecting an explicitly
> deleted column after compaction.
>
> The root cause is ReusableLivenessInfo.isExpiring(), which checked
> localExpirationTime != NO_EXPIRATION_TIME instead of ttl != NO_TTL. Both
> tombstone cells and expiring cells have a non-default localExpirationTime
> (tombstones store the deletion timestamp there) so the check returned true
> for both. This violates the LivenessInfo interface contract, which defines
> isExpiring() as "whether the info has a ttl", and diverges from the canonical
> implementation in AbstractCell.isExpiring() which correctly checks ttl() !=
> NO_TTL.
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