[LUCENE-8198] Add ability to persist deletes across merges

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 7.3, 8.0
• Lucene Fields: New
• Assignee: Simon Willnauer
• Reporter: Simon Willnauer
• Created: 11/Mar/18 21:05
• Updated: 14/Mar/18 08:26
• Resolved: 14/Mar/18 08:26

Description

This allows conditionally persist deletes on a per document basis to prevent them from being merged away. This expert feature is useful to maintain history of documents in the index where otherwise a duplicate storage mechanism would be needed. For instance features like CouchDBs changes API can be build on top of persistent deletes. While using persistent deletes has a considerably small overhead at merge time or when deletes applied to fully deleted segments, there is no impact if persistent deletes are unused.