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Posted to issues-all@impala.apache.org by "Kurt Deschler (Jira)" <ji...@apache.org> on 2021/10/11 18:27:00 UTC

[jira] [Commented] (IMPALA-10961) Implement 3-way quicksort in sorter

    [ https://issues.apache.org/jira/browse/IMPALA-10961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17427303#comment-17427303 ] 

Kurt Deschler commented on IMPALA-10961:
----------------------------------------

See attachments for standalone sorter code testing program with base implementation of 3-way quicksort.

> Implement 3-way quicksort in sorter
> -----------------------------------
>
>                 Key: IMPALA-10961
>                 URL: https://issues.apache.org/jira/browse/IMPALA-10961
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Csaba Ringhofer
>            Assignee: Noemi Pap-Takacs
>            Priority: Major
>              Labels: performance
>         Attachments: checksorted.patch, qsort.cc
>
>
> Using 3-way partitioning in quicksort could massively speed up sorting if there is a large number of duplicate elements. This is very common in sorts before partitioned inserts.



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