[jira] [Updated] (ARROW-8164) [C++][Dataset] Let datasets be viewable with non-identical schema

["Wes McKinney (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8164?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney updated ARROW-8164:
--------------------------------
    Fix Version/s:     (was: 1.0.0)
                   0.17.0

> [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: 2h 40m
>  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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