| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.lucene.search; |
| |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.Comparator; |
| import java.util.List; |
| |
| import org.apache.lucene.index.LeafReaderContext; |
| |
| import static org.apache.lucene.search.TopDocsCollector.EMPTY_TOPDOCS; |
| |
| /** |
| * Optimized collector for large number of hits. |
| * The collector maintains an ArrayList of hits until it accumulates |
| * the requested number of hits. Post that, it builds a Priority Queue |
| * and starts filtering further hits based on the minimum competitive |
| * score. |
| */ |
| public final class LargeNumHitsTopDocsCollector implements Collector { |
| private final int requestedHitCount; |
| private List<ScoreDoc> hits = new ArrayList<>(); |
| // package private for testing |
| HitQueue pq; |
| ScoreDoc pqTop; |
| int totalHits; |
| |
| public LargeNumHitsTopDocsCollector(int requestedHitCount) { |
| this.requestedHitCount = requestedHitCount; |
| this.totalHits = 0; |
| } |
| |
| // We always return COMPLETE since this collector should ideally |
| // be used only with large number of hits case |
| @Override |
| public ScoreMode scoreMode() { |
| return ScoreMode.COMPLETE; |
| } |
| |
| @Override |
| public LeafCollector getLeafCollector(LeafReaderContext context) { |
| final int docBase = context.docBase; |
| return new TopScoreDocCollector.ScorerLeafCollector() { |
| |
| @Override |
| public void setScorer(Scorable scorer) throws IOException { |
| super.setScorer(scorer); |
| } |
| |
| @Override |
| public void collect(int doc) throws IOException { |
| float score = scorer.score(); |
| |
| // This collector relies on the fact that scorers produce positive values: |
| assert score >= 0; // NOTE: false for NaN |
| |
| if (totalHits < requestedHitCount) { |
| hits.add(new ScoreDoc(doc + docBase, score)); |
| totalHits++; |
| return; |
| } else if (totalHits == requestedHitCount) { |
| // Convert the list to a priority queue |
| |
| // We should get here only when priority queue |
| // has not been built |
| assert pq == null; |
| assert pqTop == null; |
| pq = new HitQueue(requestedHitCount, false); |
| |
| for (ScoreDoc scoreDoc : hits) { |
| pq.add(scoreDoc); |
| } |
| |
| pqTop = pq.top(); |
| hits = null; |
| } |
| |
| if (score > pqTop.score) { |
| pqTop.doc = doc + docBase; |
| pqTop.score = score; |
| pqTop = pq.updateTop(); |
| } |
| ++totalHits; |
| } |
| }; |
| } |
| |
| /** Returns the top docs that were collected by this collector. */ |
| public TopDocs topDocs(int howMany) { |
| |
| if (howMany <= 0 || howMany > totalHits) { |
| throw new IllegalArgumentException("Incorrect number of hits requested"); |
| } |
| |
| ScoreDoc[] results = new ScoreDoc[howMany]; |
| |
| // Get the requested results from either hits list or PQ |
| populateResults(results, howMany); |
| |
| return newTopDocs(results); |
| } |
| |
| /** |
| * Populates the results array with the ScoreDoc instances. This can be |
| * overridden in case a different ScoreDoc type should be returned. |
| */ |
| protected void populateResults(ScoreDoc[] results, int howMany) { |
| if (pq != null) { |
| assert totalHits >= requestedHitCount; |
| for (int i = howMany - 1; i >= 0; i--) { |
| results[i] = pq.pop(); |
| } |
| return; |
| } |
| |
| // Total number of hits collected were less than requestedHitCount |
| assert totalHits < requestedHitCount; |
| Collections.sort(hits, Comparator.comparing((ScoreDoc scoreDoc) -> |
| scoreDoc.score).reversed().thenComparing(scoreDoc -> scoreDoc.doc)); |
| |
| for (int i = 0; i < howMany; i++) { |
| results[i] = hits.get(i); |
| } |
| } |
| |
| /** |
| * Returns a {@link TopDocs} instance containing the given results. If |
| * <code>results</code> is null it means there are no results to return, |
| * either because there were 0 calls to collect() or because the arguments to |
| * topDocs were invalid. |
| */ |
| protected TopDocs newTopDocs(ScoreDoc[] results) { |
| return results == null ? EMPTY_TOPDOCS : new TopDocs(new TotalHits(totalHits, TotalHits.Relation.EQUAL_TO), results); |
| } |
| |
| /** Returns the top docs that were collected by this collector. */ |
| public TopDocs topDocs() { |
| return topDocs(Math.min(totalHits, requestedHitCount)); |
| } |
| } |