[jira] [Commented] (ARROW-5409) [C++] Improvement for IsIn Kernel when right array is small

["Antoine Pitrou (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-5409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17239285#comment-17239285 ] 

Antoine Pitrou commented on ARROW-5409:
---------------------------------------

[~david1437] Would you like to submit a PR so that we can iterate on this?

> [C++] Improvement for IsIn Kernel when right array is small
> -----------------------------------------------------------
>
>                 Key: ARROW-5409
>                 URL: https://issues.apache.org/jira/browse/ARROW-5409
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Preeti Suman
>            Assignee: David Sherrier
>            Priority: Major
>             Fix For: 3.0.0
>
>         Attachments: set_lookup_benchmark
>
>
> The core of the algorithm (as python) is 
> {code:java}
> for idx, elem in array:
>   output[i] = (elem in memo_table)
> {code}
>  Often the right operand list will be very small, in this case, the hashtable should be replaced with a constant vector. 



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