[LUCENE-9314] Lucene monitor module uses ByteBuffersDirectory rather than MemoryIndex when matching a single document

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 8.2, 8.3, 8.4, 8.5
• Fix Version/s: 8.6
• Component/s: modules/other
• Labels: easyfix performance pull-request-available
• Lucene Fields: New
• Assignee: Alan Woodward
• Reporter: Pierre-Luc Perron
• Created: 10/Apr/20 14:31
• Updated: 28/Aug/22 16:01
• Resolved: 27/Apr/20 09:51

Description

Lucene monitor function, match single document, wraps a single document into a array of documents. Hence, it always calls the function, match many documents,  which builds a MultiDocumentBatch rather than a SingletonDocumentBatch. The former uses ByteBuffersDirectory while later uses MemoryIndex.

As per documentation, MemoryIndex is a high-performance single-document main memory Apache Lucene fulltext search index. Hence, Lucene monitor should use it when matching a single document.

The patch routes match single document to a SingletonDocumentBatch.

Issue Links

• links to: GitHub Pull Request #1423