[jira] [Commented] (ARROW-12606) [C++] Quantile function failing on list scalars.

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

    [ https://issues.apache.org/jira/browse/ARROW-12606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17338330#comment-17338330 ] 

Joris Van den Bossche commented on ARROW-12606:
-----------------------------------------------

I think the underlying reason is that {{quantile}} doesn't correct handle arrays with an offset, as this simpler example also fails:

{code}
In [10]: arr = pa.array([1, 2])

In [11]: pc.quantile(arr)
Out[11]: 
<pyarrow.lib.DoubleArray object at 0x7fdd8410e940>
[
  1.5
]

In [12]: pc.quantile(arr[1:])
Out[12]: 
<pyarrow.lib.DoubleArray object at 0x7fdd7f7a1280>
[
  1.44115e+17
]
{code}

and the list scalar's {{values}} is a offsetted view of the parent ListArray.values

> [C++] Quantile function failing on list scalars.
> ------------------------------------------------
>
>                 Key: ARROW-12606
>                 URL: https://issues.apache.org/jira/browse/ARROW-12606
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++, Python
>    Affects Versions: 4.0.0
>         Environment: macOS, ubuntu
>            Reporter: A. Coady
>            Assignee: Yibo Cai
>            Priority: Major
>
> Sounds unrelated, but it's the simplest example I've gotten to reproduce.
>  
> {code:java}
> import pyarrow as pa, pyarrow.compute as pc 
> array = pa.array([[0], [1]])
> first, second = [pc.quantile(scalar.values) for scalar in array]
> assert first.to_pylist() == [0]
> assert (second.to_pylist() == [1]), second # 7.20576e+16{code}



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