[ARROW-15118] [C++] Avoid bitmap buffer if all inputs are all valid for Scalar Kernels

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 8.0.0
• Component/s: C++
• Labels: good-second-issue kernel pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/30628
• Assignee: Pradeep Garigipati
• Reporter: Eduardo Ponce
• Created: 15/Dec/21 16:24
• Updated: 11/Jan/23 08:44
• Resolved: 01/Mar/22 13:14

Description

Cast kernels seem to always create and populate the null bitmap even if the input data structure had a nullptr null bitmap. This automatic and extra allocation is not desirable, and not consistent.

It seems some cast kernels use COMPUTED_NO_PREALLOCATE and others use the default (INTERSECTION). We could change INTERSECTION to be a general case where if all inputs have no nulls, then a null bitmap should not be emitted.

Issue Links

• links to: GitHub Pull Request #12080