[ARROW-15455] [C++] Cast between fixed size list type and variable size list

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++
• Labels: good-second-issue kernel pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20086
• Assignee: Unassigned
• Reporter: Joris Van den Bossche
• Created: 25/Jan/22 19:20
• Updated: 11/Jan/23 11:37

Description

Casting from fixed size list to variable size list could be possible, I think, but currently doesn't work:

>>> fixed_size = pa.array([[1, 2], [3, 4]], type=pa.list_(pa.int64(), 2))
>>> fixed_size.cast(pa.list_(pa.int64()))
...
ArrowNotImplementedError: Unsupported cast from fixed_size_list<item: int64>[2] to list using function cast_list

And in principle, a cast the other way around could also be possible if it is checked that each list has the correct length.

Issue Links

• links to: GitHub Pull Request #12517