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https://issues.apache.org/jira/browse/CASSANDRA-8979?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Oleg Anastasyev updated CASSANDRA-8979:
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Attachment: 8979-AvoidBufferAllocation-2.0_patch.txt
Noticed an unneccessary ByteBuffer allocation in PrecompactedRow in case it
does not updates a digest.
Attached a patch that avoids it.
> MerkleTree mismatch for deleted and non-existing rows
> -----------------------------------------------------
>
> Key: CASSANDRA-8979
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8979
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Stefan Podkowinski
> Assignee: Stefan Podkowinski
> Fix For: 2.1.4, 2.0.14
>
> Attachments: 8979-AvoidBufferAllocation-2.0_patch.txt,
> cassandra-2.0-8979-lazyrow_patch.txt, cassandra-2.0-8979-validator_patch.txt,
> cassandra-2.0-8979-validatortest_patch.txt,
> cassandra-2.1-8979-lazyrow_patch.txt, cassandra-2.1-8979-validator_patch.txt
>
>
> Validation compaction will currently create different hashes for rows that
> have been deleted compared to nodes that have not seen the rows at all or
> have already compacted them away.
> In case this sounds familiar to you, see CASSANDRA-4905 which was supposed to
> prevent hashing of expired tombstones. This still seems to be in place, but
> does not address the issue completely. Or there was a change in 2.0 that
> rendered the patch ineffective.
> The problem is that rowHash() in the Validator will return a new hash in any
> case, whether the PrecompactedRow did actually update the digest or not. This
> will lead to the case that a purged, PrecompactedRow will not change the
> digest, but we end up with a different tree compared to not having rowHash
> called at all (such as in case the row already doesn't exist).
> As an implication, repair jobs will constantly detect mismatches between
> older sstables containing purgable rows and nodes that have already compacted
> these rows. After transfering the reported ranges, the newly created sstables
> will immediately get deleted again during the following compaction. This will
> happen for each repair run over again until the sstable with the purgable row
> finally gets compacted.
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