[jira] [Commented] (ARROW-10640) [C++] A "where" kernel to combine two arrays based on a mask

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-10640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17259143#comment-17259143 ] 

Joris Van den Bossche commented on ARROW-10640:
-----------------------------------------------

Note there is some discussion about this on https://github.com/apache/arrow/pull/9024

> [C++] A "where" kernel to combine two arrays based on a mask
> ------------------------------------------------------------
>
>                 Key: ARROW-10640
>                 URL: https://issues.apache.org/jira/browse/ARROW-10640
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Joris Van den Bossche
>            Priority: Major
>
> (from discussion in ARROW-9489 with [~maartenbreddels])
> A general "where" kernel like {{np.where}} (https://numpy.org/doc/stable/reference/generated/numpy.where.html) seems a generally useful kernel to have, and could also help mimicking some other python (setitem-like) operations. 
> The concrete use case in ARROW-9489 is to basically do a {{fill_null(array[string], array[string])}} which could be expressed as {{where(is_null(arr), arr2, arr)}}. 



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