[ARROW-4095] [C++] Implement optimizations for dictionary unification where dictionaries are prefixes of the unified dictionary

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.15.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20688
• Assignee: Antoine Pitrou
• Reporter: Wes McKinney
• Created: 21/Dec/18 00:36
• Updated: 11/Jan/23 07:31
• Resolved: 31/Aug/19 04:43

Description

In the event that the unified dictionary contains other dictionaries as prefixes (e.g. as the result of delta dictionaries), we can avoid memory allocation and index transposition.

See discussion at

https://github.com/apache/arrow/pull/3165#discussion_r243020982

Issue Links

• links to: GitHub Pull Request #5230