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https://issues.apache.org/jira/browse/CASSANDRA-21555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jon Haddad reassigned CASSANDRA-21555:
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Assignee: Jon Haddad
> Reduce repair overhead on tables with large partitions (20GB+)
> --------------------------------------------------------------
>
> Key: CASSANDRA-21555
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21555
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Feature/Repair
> Reporter: Jon Haddad
> Assignee: Jon Haddad
> Priority: Normal
>
> When repair streams a large partition (20GB+) to rebuild it on the receiving
> side, the SSTable writer that constructs the partition's row index grows its
> internal buffer incrementally rather than sizing it up front. For a partition
> that size, this results in a very large amount of unnecessary memory copying
> and discarded garbage, adding significant CPU time and GC pressure on top of
> the write itself.
> We can avoid that overhead by sizing the buffer correctly ahead of time and
> backing it with reused off-heap memory instead of repeatedly growing and
> discarding on-heap arrays. It does not change what data is streamed or how
> repair diffs partitions — it only reduces the cost of writing out a large
> partition once that data is already being transferred.
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