[LUCENE-2447] Add support for subsets of searchables inside a MultiSearcher/ParallelMultiSearcher instance's methods at runtime

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 3.0.1
• Component/s: core/search
• Labels: multisearcher parallelmultisearcher

Environment

Irrelevant

• Lucene Fields: New, Patch Available
• Assignee: Unassigned
• Reporter: Edward Drapkin
• Created: 05/May/10 17:39
• Updated: 28/Aug/22 12:26

Description

Here's the situation: We have a site with a fair few amount of indexes that we're using MultiSearcher/ParallelMultiSearcher for, but the users can select an arbitrary permutation of indexes to search. For example (contrived, but illustratory): the site has indexes numbered 1 - 10; user A wants to search in all 10; user B wants to search indexes 1, 2 and 3, user C wants to search even-numbered indexes. From Lucene 3.0.1, the only way to do this is to continually instantiate a new MultiSearcher based on every permutation of indexes that a user wants, which is not ideal at all.

What I've done is add a new parameter to all methods in MultiSearcher that use the searchables array (docFreq, search, rewrite and createDocFrequencyMap), a Set<Searchable> which is checked for isEmpty() and contains() for every iteration over the searchables[]. The actual logic has been moved into these methods and the old methods have become overloads that pass a Collections.emptySet() into those methods, so I do not expect there to be a very noticeable performance impact as a result of this modification, if it's measurable at all.

I didn't modify the test for MultiSearcher very much, just enough to illustrate the that subsetting of the search results works, since no other logic has changed. If I need to do more for the testing, let me know and I'll do it.

I've attached the patches for MultiSearcher.java, ParallelMultiSearcher.java and TestMultiSearcher.java.