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https://issues.apache.org/jira/browse/ARROW-18265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17641015#comment-17641015
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Weston Pace commented on ARROW-18265:
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Ok. I think I understand now. The problem isn't how the user expresses it but
more how we construct a FieldPath / FieldRef for one of these pseudo-refs. I
don't think we rely on the child referencing behavior for variable length lists
anywhere today so it's probably ok in that sense.
However, it would be a bit tricky if FindOne/FindAll ended up calling
list_element (a compute function). FindOne/FindAll currently is in the core
module and not the compute module. That being said we don't really distinguish
between the two and I think have all but accepted they are co-mingled.
> [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
> Labels: pull-request-available
> Fix For: 11.0.0
>
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> {{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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