[ARROW-1741] [C++] Comparison function for DictionaryArray to determine if indices are "compatible"

• Type: New Feature
• 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/17745
• Assignee: Ben Kietzman
• Reporter: Wes McKinney
• Created: 26/Oct/17 22:37
• Updated: 11/Jan/23 07:16
• Resolved: 14/Sep/19 22:34

Description

For example, if one array's dictionary is larger than the other, but the overlapping beginning portion is the same, then the respective dictionary indices correspond to the same values. Therefore, in analytics, one may choose to drop the smaller dictionary in favor of the larger dictionary, and this need not incur any computational overhead (beyond comparing the dictionary prefixes – there may be some way to engineer "dictionary lineage" to make this comparison even cheaper)

Issue Links

• links to: GitHub Pull Request #5342