[LUCENE-8965] ConcurrentMergeScheduler should maybe sometimes do synchronously

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Component/s: core/index
• Lucene Fields: New
• Assignee: David Smiley
• Reporter: David Smiley
• Created: 04/Sep/19 18:48
• Updated: 28/Aug/22 15:50
• Resolved: 21/Jun/20 23:59

Description

It can be beneficial for the ConcurrentMergeScheduler to sometimes not do concurrent merges (i.e. sometimes do a serial merge). When the provided "OneMerge" is small and when the MergeTrigger is FULL_FLUSH (i.e. on a commit), a new searcher would benefit from seeing fewer segments. If index replication is used, this setting can reduce the net replication by merging a little more eagerly sometimes.

Issue Links

• relates to: LUCENE-8962 Can we merge small segments during refresh, for faster searching?
• links to: GitHub Pull Request #856