[ARROW-8788] [C#] Array builders to use bit-packed buffer builder rather than boolean array builder for validity map

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.17.0
• Fix Version/s: 1.0.0
• Component/s: C#
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/24934
• Assignee: Unassigned
• Reporter: Adam Szmigin
• Created: 13/May/20 14:34
• Updated: 11/Jan/23 08:02
• Resolved: 10/Jun/20 13:59

Description

The C# array builders were recently enhanced to have support for adding nullable values easily, under PR #7032.

However, the builders internally referenced BooleanArray.Builder, which itself then had logic "baked-in" for efficient bit-packing of boolean values into a byte buffer.

It would be cleaner for there to be a general-purpose bit-packed buffer builder, and for all array builders to use that for their validity map. The boolean array builder would use it twice: once for values, once for validity.

Issue Links

• relates to: ARROW-6603 [C#] ArrayBuilder API to support writing nulls
• supercedes: ARROW-5035 [C#] ArrowBuffer.Builder<bool> is broken
• links to: GitHub Pull Request #7158