[LUCENE-8068] Allow IndexWriter to write a single DWPT to disk

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 7.2, 8.0
• Lucene Fields: New, Patch Available
• Assignee: Unassigned
• Reporter: Simon Willnauer
• Created: 27/Nov/17 21:36
• Updated: 28/Aug/22 15:22
• Resolved: 30/Nov/17 18:00

Description

Today we IW can only flush a DWPT to disk if an external resource calls flush() or refreshes a NRT reader or if a DWPT is selected as flush pending. Yet, the latter has the problem that it always ties up an indexing thread and if flush / NRT refresh is called a whole bunch of indexing threads is tied up. If IW could offer a simple `flushNextBuffer()` method that synchronously flushes the next pending or biggest active buffer to disk memory could be controlled in a more fine granular fashion from outside of the IW. This is for instance useful if more than one IW (shards) must be maintained in a single JVM / system.

Issue Links

• breaks: LUCENE-8079 TestTopFieldCollectorEarlyTermination.testEarlyTermination() failures