[ARROW-10449] [Rust] Make dictionary keys be a PrimitiveArray

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 3.0.0
• Component/s: Rust
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26426
• Assignee: Jorge Leitão
• Reporter: Jorge Leitão
• Created: 31/Oct/20 06:56
• Updated: 11/Jan/23 08:13
• Resolved: 07/Nov/20 12:42

Description

Currently, dictionary keys use a NullIterator to iterate them. However, physically, they are fully allocated in memory and are interpretable as a PrimitiveArray.

This issue's main purpose is to have `keys` return a `PrimitiveArray`, so that users can use it as any other array.

This will also allow to remove `NullIter`.

Issue Links

• links to: GitHub Pull Request #8561