[ARROW-16607] [R] Improve KeyValueMetadata handling

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 9.0.0
• Component/s: R
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/31961
• Assignee: Neal Richardson
• Reporter: Neal Richardson
• Created: 18/May/22 14:33
• Updated: 11/Jan/23 11:45
• Resolved: 26/May/22 17:14

Description

Followup to ARROW-15271. Among the objectives:

• Push KVM handling in ExecPlan so that Run() preserves the R metadata we want; also remove the duplicate handling of it for Write()
• Better encapsulate KVM for the the $metadata and $r_metadata so that as a user/developer, you never have to touch the serialize/deserialize functions, you just have a list to work with
• Factor out a common utility in r/src for taking cpp11::strings (named character vector) and producing arrow::KeyValueMetadata

Issue Links

• links to: GitHub Pull Request #13210