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Posted to commits@cassandra.apache.org by "Richard Low (JIRA)" <ji...@apache.org> on 2014/12/03 18:20:12 UTC

[jira] [Created] (CASSANDRA-8414) Compaction is O(n^2) when deleting lots of tombstones

Richard Low created CASSANDRA-8414:
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             Summary: Compaction is O(n^2) when deleting lots of tombstones
                 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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