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https://issues.apache.org/jira/browse/KUDU-2253?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved KUDU-2253.
-------------------------------
Resolution: Fixed
Assignee: Dan Burkert
Fix Version/s: 1.7.0
Dan fixed in 8058825ba8cd02897e0a1b592d74bdfe6e2a3f62
> Deltafile on-disk size is 3x larger than expected for large-value workloads
> ---------------------------------------------------------------------------
>
> Key: KUDU-2253
> URL: https://issues.apache.org/jira/browse/KUDU-2253
> Project: Kudu
> Issue Type: Bug
> Components: tablet
> Affects Versions: 1.6.0
> Reporter: Dan Burkert
> Assignee: Dan Burkert
> Priority: Major
> Fix For: 1.7.0
>
>
> While looking into the performance of the integration test written for
> KUDU-2251 (https://gerrit.cloudera.org/#/c/8951/ revision 6), Todd and I
> found that the on-disk deltafiles written are about 3x larger than expected.
> The culprit is an optimization in the CFile value index which is [turned off
> for delta
> files|https://github.com/apache/kudu/blob/branch-1.6.x/src/kudu/tablet/deltafile.cc#L106-L107].
> The optimization truncates large keys after the first unique byte between
> sequential values. The deltafile values, in the case of this integration
> test, include the small {{DeltaKey}}, and the 8KiB updated value. As a
> result the BTree interior nodes are being completely filled by only ~4 values
> ([32KiB cblock size by
> default|https://github.com/apache/kudu/blob/branch-1.6.x/src/kudu/tablet/deltafile.cc#L58-L60]).
> This makes the BTree far less effective, and means that the full updated
> data is written many times. We expect fixing this will improve performance
> for update-heavy workloads with large values (for example YCSB).
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