[ARROW-4097] [C++] Add function to "conform" a dictionary array to a target new dictionary

• Type: New Feature
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++
• External issue URL: https://github.com/apache/arrow/issues/20690
• Assignee: Unassigned
• Reporter: Wes McKinney
• Created: 21/Dec/18 00:41
• Updated: 11/Jan/23 07:31

Description

Follow up work to ARROW-554.

Unifying multiple dictionary-encoded arrays is one use case. Another is rewriting a DictionaryArray to be based on another dictionary. For example, this would be used to implement Cast from one dictionary type to another.

This will need to be able to insert nulls where there are values that are not found in the target dictionary

see also discussion at https://github.com/apache/arrow/pull/3165#discussion_r243025730

Issue Links

• is a child of: ARROW-8894 [C++] C++ array kernels framework and execution buildout (umbrella issue)
• relates to: ARROW-1574 [C++] Implement kernel function that converts a dense array to dictionary given known dictionary