[jira] [Commented] (ARROW-6923) [C++] Option for Filter kernel how to handle nulls in the selection vector

["Neal Richardson (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-6923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17133757#comment-17133757 ] 

Neal Richardson commented on ARROW-6923:
----------------------------------------

Duplicate of ARROW-8216?

> [C++] Option for Filter kernel how to handle nulls in the selection vector
> --------------------------------------------------------------------------
>
>                 Key: ARROW-6923
>                 URL: https://issues.apache.org/jira/browse/ARROW-6923
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Joris Van den Bossche
>            Priority: Major
>             Fix For: 1.0.0
>
>
> How nulls are handled in the boolean mask (selection vector) in a filter kernel varies between languages / data analytics systems (e.g. base R propagates nulls, dplyr R skips (sees as False), SQL generally skips them as well I think, Julia raises an error).
> Currently, in Arrow C++ we "propagate" nulls (null in the selection vector gives a null in the output):
> {code}
> In [7]: arr = pa.array([1, 2, 3]) 
> In [8]: mask = pa.array([True, False, None]) 
> In [9]: arr.filter(mask) 
> Out[9]: 
> <pyarrow.lib.Int64Array object at 0x7fefe44b3048>
> [
>   1,
>   null
> ]
> {code}
> Given the different ways this could be done (propagate, skip, error), should we provide an option to control this behaviour?



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