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Richard Low commented on CASSANDRA-8414: ---------------------------------------- I tested this on some real workload SSTables and got a 2x speedup on force compaction! Also the output was the same as before. Can someone commit the patch? > 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 MÃ¥rdell > Labels: performance > Fix For: 2.0.12, 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, > cassandra-2.1-8414-5.txt, cassandra-2.1-8414-6.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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)