[ARROW-10207] [C++] Unary kernels that results in a list have no preallocated offset buffer

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26211
• Assignee: Antoine Pitrou
• Reporter: Maarten Breddels
• Created: 07/Oct/20 09:13
• Updated: 11/Jan/23 08:11
• Resolved: 22/Oct/20 18:49

Description

I noticed in

https://github.com/apache/arrow/pull/8271

That a string->list[string] kernel does not have the offsets preallocated in the output. I believe there is a preference for not doing allocations in kernels, so this can be optimized at a higher level. I think it can also be done in this case. 

Issue Links

• links to: GitHub Pull Request #8498