Ben Kietzman created ARROW-11981:
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Summary: [C++][Dataset][Compute] Replace UnionDataset with Union
ExecNode
Key: ARROW-11981
URL: https://issues.apache.org/jira/browse/ARROW-11981
Project: Apache Arrow
Issue Type: Improvement
Components: C++
Affects Versions: 3.0.0
Reporter: Ben Kietzman
UnionDataset allows Fragments of multiple schemas and differing file formats to
be scanned together as a single Dataset. This is useful functionality but makes
the Dataset interface somewhat difficult to reason about since it must be
general enough to accommodate UnionDataset.
After ARROW-11928 it will probably be more natural to support unioning of
datasets through a subclass of ExecNode. Reconciliation of differing schemas
can then be trivially handled by a full ProjectNode.
Note this would obviate both ARROW-11001 and ARROW-11749. In addition, Dataset
could be simplified to a concrete class containing a set of compatibly
typed/formatted Fragments.
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