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https://issues.apache.org/jira/browse/ARROW-15089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17458784#comment-17458784
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David Li commented on ARROW-15089:
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This also would be useful to implement [one type of field references in
Substrait|https://substrait.io/expressions/field_references/]; also see
ARROW-14658 et. al.
> [C++] Add compute kernel to get MapArray value for given key
> ------------------------------------------------------------
>
> Key: ARROW-15089
> URL: https://issues.apache.org/jira/browse/ARROW-15089
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Affects Versions: 6.0.1
> Reporter: Will Jones
> Priority: Major
> Labels: C++, Kernels, beginner, compute, good-second-issue,
> kernel
>
> Given a "map", an obvious operation is to get an item corresponding to a key.
> The idea here is to create a kernel that does this for each map in the array.
> IIRC MapArray isn't guaranteed to have unique keys. So one version would
> return an array of ItemType by returning the first of last item for a given
> key. Yet another version could return a ListType containing all matching
> items.
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