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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2011/09/21 05:55:08 UTC

[jira] [Commented] (CASSANDRA-3234) LeveledCompaction has several performance problems

    [ https://issues.apache.org/jira/browse/CASSANDRA-3234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13109244#comment-13109244 ] 

Jonathan Ellis commented on CASSANDRA-3234:
-------------------------------------------

split OneToOne classes into separate patches and fixed bug in estimated tables calculation

> LeveledCompaction has several performance problems
> --------------------------------------------------
>
>                 Key: CASSANDRA-3234
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3234
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 1.0.0
>
>         Attachments: 0001-optimize-single-source-case-for-MergeIterator.txt, 0002-add-TrivialOneToOne-optimization.txt, 0003-fix-leveled-BF-size-calculation.txt
>
>
> Two main problems:
> - BF size calculation doesn't take into account LCS breaking the output apart into "bite sized" sstables, so memory use is much higher than predicted
> - ManyToMany merging is slow.  At least part of this is from running the full reducer machinery against single input sources, which can be optimized away.

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