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https://issues.apache.org/jira/browse/ARROW-1741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16845961#comment-16845961
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Wes McKinney commented on ARROW-1741:
-------------------------------------
Now that we have variable dictionaries in C++, having a function to determine
if two DictionaryArrays can be compared without a unification step would be
useful.
> [C++] Comparison function for DictionaryArray to determine if indices are
> "compatible"
> --------------------------------------------------------------------------------------
>
> Key: ARROW-1741
> URL: https://issues.apache.org/jira/browse/ARROW-1741
> Project: Apache Arrow
> Issue Type: New Feature
> Components: C++
> Reporter: Wes McKinney
> Priority: Major
> Fix For: 0.14.0
>
>
> For example, if one array's dictionary is larger than the other, but the
> overlapping beginning portion is the same, then the respective dictionary
> indices correspond to the same values. Therefore, in analytics, one may
> choose to drop the smaller dictionary in favor of the larger dictionary, and
> this need not incur any computational overhead (beyond comparing the
> dictionary prefixes -- there may be some way to engineer "dictionary lineage"
> to make this comparison even cheaper)
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