[jira] [Commented] (CASSANDRA-15511) Utilising BTree Improvements

["Benedict Elliott Smith (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-15511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17017495#comment-17017495 ] 

Benedict Elliott Smith commented on CASSANDRA-15511:
----------------------------------------------------

[3.0|https://github.com/belliottsmith/cassandra/tree/15511]

> Utilising BTree Improvements
> ----------------------------
>
>                 Key: CASSANDRA-15511
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15511
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local/Other
>            Reporter: Benedict Elliott Smith
>            Assignee: Benedict Elliott Smith
>            Priority: Normal
>
> This patch utilises CASSANDRA-15510 to improve throughput and reduce garbage produced by a number of common operations, by employing {{transformAndFilter}}, {{transform}} and {{FastBuilder}}
> * {{Row}}, {{Cell}} and {{ComplexColumnData}} cloning are implemented with {{BTree.transform}}, so no special builders are necessary; 
> ** {{Rows.copy}} removed
> * {{Rows.merge}} implemented using {{BTree.update}} and a {{ColumnData}} reconciler
> ** Zero-allocations if result of merge is same as {{existing}}
> ** Fewer comparisons
> * {{ColumnData}} reconciler implemented in same manner
> ** {{Cells.reconcileComplex}} is retired
> ** {{ComplexColumnData}} reconciliation now
> *** Garbage-free if the merge has no effect
> *** Always fewer allocations
> *** Fewer comparisons
> * {{FastBuilder}} employed widely:
> ** {{ClusteringIndexNamesFilter}} deserialization
> ** {{Columns}} deserialization
> ** {{PartitionUpdate}} deserialization
> ** {{AbstractBTreePartition}} construction
> ** Misc others
> The upshot of this work when combined with the proposed patch for CASSANDRA-15367 has a dramatic impact on operations over collection types - under contention, as much as 100x improved throughput, and hundreds of megabytes of reduced allocations.  For all operations, allocations under contention and no contention are significantly reduced and throughput improved.
> I am still awaiting the final results of the comprehensive performance comparison for {{AtomicBTreePartition}}, after which I will establish what impact there might be on compaction and normal reads, both of which should be affected by this patch.



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