[ARROW-11749] [C++][Dataset] Support projections between children of UnionDatasets

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.0.0
• Component/s: C++
• Labels: dataset
• External issue URL: https://github.com/apache/arrow/issues/18529
• Assignee: Unassigned
• Reporter: Ben Kietzman
• Created: 23/Feb/21 20:12
• Updated: 11/Jan/23 08:21

Description

ARROW-11174 adds support for arbitrary expressions in projection. It'd be useful to have that power when unifying disparate child datasets. For example, even the simple case where a column is renamed in a newer data file currently cannot be accommodated.