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Posted to commits@cassandra.apache.org by "Benedict (JIRA)" <ji...@apache.org> on 2014/12/03 21:27:13 UTC

[jira] [Updated] (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:all-tabpanel ]

Benedict updated CASSANDRA-8414:
--------------------------------
    Summary: Avoid loops over array backed iterators that call iter.remove()  (was: Compaction is O(n^2) when deleting lots of tombstones)

> 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: Bug
>          Components: Core
>            Reporter: Richard Low
>
> 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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