quick exit on filter query matching no docs when rewriting knn query

[bugmakerrrrrr]

Description

[jpountz]

Can you help me understand what work this change helps save?

[bugmakerrrrrr]

Can you help me understand what work this change helps save?

Thanks for your reply. I think if the filter query matches no docs, the knn query must also match no docs. Before this small change, we always executed search tasks for each leaf reader even if the filter query is MatchNoDocsQuery.

lucene/lucene/core/src/java/org/apache/lucene/search/AbstractKnnVectorQuery.java

Lines 89 to 98 in a7ff87f

	TimeLimitingKnnCollectorManager knnCollectorManager =
	new TimeLimitingKnnCollectorManager(
	getKnnCollectorManager(k, indexSearcher), indexSearcher.getTimeout());
	TaskExecutor taskExecutor = indexSearcher.getTaskExecutor();
	List<LeafReaderContext> leafReaderContexts = reader.leaves();
	List<Callable<TopDocs>> tasks = new ArrayList<>(leafReaderContexts.size());
	for (LeafReaderContext context : leafReaderContexts) {
	tasks.add(() -> searchLeaf(context, filterWeight, knnCollectorManager));
	}
	TopDocs[] perLeafResults = taskExecutor.invokeAll(tasks).toArray(TopDocs[]::new);

[jpountz]

Thank you, that makes sense. So in the case when the filter rewrites to MatchNoDocsQuery, IndexSearcher#search would now return immediately, while it may currently need to wait for tasks to be submitted (if the queue is not empty).

Can you add a CHANGES entry?

[bugmakerrrrrr]

So in the case when the filter rewrites to MatchNoDocsQuery, IndexSearcher#search would now return immediately, while it may currently need to wait for tasks to be submitted (if the queue is not empty).

Yes, you are right.

Can you add a CHANGES entry?

Added.