[LUCENE-7537] Add multi valued field support to index sorting

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 6.4, 7.0
• Component/s: core/index
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Jim Ferenczi
• Created: 03/Nov/16 17:56
• Updated: 28/Aug/22 15:05
• Resolved: 16/Nov/16 15:38

Description

Today index sorting can be done on single valued field through the NumericDocValues (for numerics) and SortedDocValues (for strings).
I'd like to add the ability to sort on multi valued fields. Since index sorting does not accept custom comparator we could just take the minimum value of each document for an ascending sort and the maximum value for a descending sort.
This way we could handle all cases instead of throwing an exception during a merge when we encounter a multi valued DVs.