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https://issues.apache.org/jira/browse/ARROW-8164?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Neal Richardson resolved ARROW-8164.
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Resolution: Fixed
Issue resolved by pull request 6721
[https://github.com/apache/arrow/pull/6721]
> [C++][Dataset] Let datasets be viewable with non-identical schema
> -----------------------------------------------------------------
>
> Key: ARROW-8164
> URL: https://issues.apache.org/jira/browse/ARROW-8164
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++, C++ - Dataset
> Affects Versions: 0.16.0
> Reporter: Ben Kietzman
> Assignee: Ben Kietzman
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.17.0
>
> Time Spent: 3h 20m
> Remaining Estimate: 0h
>
> It would be useful to allow some schema unification capability after
> discovery has completed. For example, if a FileSystemDataset is being wrapped
> into a UnionDataset with another and their schemas are unifiable then there
> is no reason we can't create the UnionDataset (rather than emitting an error
> because the schemas are not identical).
> I think this behavior will be most naturally expressed in C++ like so:
> {code}
> virtual Result<Dataset> Dataset::ReplaceSchema(std::shared_ptr<Schema>
> schema) const = 0;
> {code}
> which will raise an error if the provided schema is not unifiable with the
> current dataset schema.
> If this needs to be extended to non trivial projections then this will
> probably warrant a separate class, {{ProjectedDataset}} or so. Definitely
> follow up material (if desired)
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