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https://issues.apache.org/jira/browse/ARROW-18265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17630176#comment-17630176
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Miles Granger commented on ARROW-18265:
---------------------------------------
Thanks [~westonpace], that's true, upon initial implementation I am using a
call to {{list_element}} so good to know I'm on the right path. :)
I'm aiming to support both variable and fixed size lists, and agree the case of
a list element not being long enough, ought to return a null.
After updating the {{struct_field}} kernel to deal with lists, it "works" for a
path specifying a 0 index, ie {{'.path.to.list[0].foo'}} but will fail if it's
{{'.path.to.list[1].foo'}} because {{FieldRef::FindOne}} doesn't discover
anything. Suspecting I need to investigate the {{FieldRef::FindAll}} visitor
implementation, but not 100% sure right now.
I'll be sure to ping you for a review once I have something worth looking at.
:-)
> [C++] Allow FieldPath to work with ListElement
> ----------------------------------------------
>
> Key: ARROW-18265
> URL: https://issues.apache.org/jira/browse/ARROW-18265
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Miles Granger
> Assignee: Miles Granger
> Priority: Major
> Fix For: 11.0.0
>
>
> {{FieldRef::FromDotPath}} can parse a single list element field. ie.
> {{{}'path.to.list[0]`{}}}but does not work in practice. Failing with:
> _struct_field: cannot subscript field of type list<....>_
> Being able to add a slice or multiple list elements is not within the scope
> of this issue.
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