[jira] [Commented] (ARROW-1565) [C++][Compute] Implement TopK/BottomK streaming execution nodes

["David Li (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-1565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17396072#comment-17396072 ] 

David Li commented on ARROW-1565:
---------------------------------

Daniel Lemire compared various approaches (modifications of the heap approach or modifications of quickselect) and found that the heap wins in his tests: https://lemire.me/blog/2017/06/21/top-speed-for-top-k-queries/ 

If we want this to perfectly emulate Pandas's nlargest/nsmallest then there are some additional complications (inputs must have a defined order to resolve ties, and/or we must be able to track and output duplicate values).

> [C++][Compute] Implement TopK/BottomK streaming execution nodes
> ---------------------------------------------------------------
>
>                 Key: ARROW-1565
>                 URL: https://issues.apache.org/jira/browse/ARROW-1565
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Wes McKinney
>            Priority: Major
>              Labels: Analytics, query-engine
>             Fix For: 6.0.0
>
>
> Heap-based topk can compute these indices in O(n log k) time



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