[ARROW-3997] [C++] [Doc] Clarify dictionary encoding integer signedness (and width?)

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.11.1
• Fix Version/s: 0.12.0
• Component/s: C++, Documentation, Format
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20599
• Assignee: Antoine Pitrou
• Reporter: Antoine Pitrou
• Created: 11/Dec/18 15:31
• Updated: 11/Jan/23 07:31
• Resolved: 09/Jan/19 22:16

Description

The Arrow spec states that a dictionary-encoded array uses int32 indices. Signed or unsigned? The spec doesn't say.

Also, the C++ implementation supports all kinds of integers as indices (8- to 64-bit, signed and unsigned). I wonder if we should at least mandate a specific signedness.

Issue Links

• links to: GitHub Pull Request #3355