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Posted to commits@cassandra.apache.org by "Richard Low (JIRA)" <ji...@apache.org> on 2015/01/07 20:31:36 UTC

[jira] [Commented] (CASSANDRA-8414) Avoid loops over array backed iterators that call iter.remove()

    [ https://issues.apache.org/jira/browse/CASSANDRA-8414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14268075#comment-14268075 ] 

Richard Low commented on CASSANDRA-8414:
----------------------------------------

+1 on 2.0 v5. Do you have a 2.1 version?

> Avoid loops over array backed iterators that call iter.remove()
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-8414
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8414
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Richard Low
>            Assignee: Jimmy Mårdell
>              Labels: performance
>             Fix For: 2.1.3
>
>         Attachments: cassandra-2.0-8414-1.txt, cassandra-2.0-8414-2.txt, cassandra-2.0-8414-3.txt, cassandra-2.0-8414-4.txt, cassandra-2.0-8414-5.txt
>
>
> I noticed from sampling that sometimes compaction spends almost all of its time in iter.remove() in ColumnFamilyStore.removeDeletedStandard. It turns out that the cf object is using ArrayBackedSortedColumns, so deletes are from an ArrayList. If the majority of your columns are GCable tombstones then this is O(n^2). The data structure should be changed or a copy made to avoid this.



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