| /* |
| * 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; |
| |
| /** |
| * Collector decouples the score from the collected doc: the score computation is skipped entirely |
| * if it's not needed. Collectors that do need the score should implement the {@link #setScorer} |
| * method, to hold onto the passed {@link Scorer} instance, and call {@link Scorer#score()} within |
| * the collect method to compute the current hit's score. If your collector may request the score |
| * for a single hit multiple times, you should use {@link ScoreCachingWrappingScorer}. |
| * |
| * <p><b>NOTE:</b> The doc that is passed to the collect method is relative to the current reader. |
| * If your collector needs to resolve this to the docID space of the Multi*Reader, you must re-base |
| * it by recording the docBase from the most recent setNextReader call. Here's a simple example |
| * showing how to collect docIDs into a BitSet: |
| * |
| * <pre class="prettyprint"> |
| * IndexSearcher searcher = new IndexSearcher(indexReader); |
| * final BitSet bits = new BitSet(indexReader.maxDoc()); |
| * searcher.search(query, new Collector() { |
| * |
| * public LeafCollector getLeafCollector(LeafReaderContext context) |
| * throws IOException { |
| * final int docBase = context.docBase; |
| * return new LeafCollector() { |
| * |
| * <em>// ignore scorer</em> |
| * public void setScorer(Scorer scorer) throws IOException { |
| * } |
| * |
| * public void collect(int doc) throws IOException { |
| * bits.set(docBase + doc); |
| * } |
| * |
| * }; |
| * } |
| * |
| * }); |
| * </pre> |
| * |
| * <p>Not all collectors will need to rebase the docID. For example, a collector that simply counts |
| * the total number of hits would skip it. |
| * |
| * @lucene.experimental |
| */ |
| public interface LeafCollector { |
| |
| /** |
| * Called before successive calls to {@link #collect(int)}. Implementations that need the score of |
| * the current document (passed-in to {@link #collect(int)}), should save the passed-in Scorer and |
| * call scorer.score() when needed. |
| */ |
| void setScorer(Scorable scorer) throws IOException; |
| |
| /** |
| * Called once for every document matching a query, with the unbased document number. |
| * |
| * <p>Note: The collection of the current segment can be terminated by throwing a {@link |
| * CollectionTerminatedException}. In this case, the last docs of the current {@link |
| * org.apache.lucene.index.LeafReaderContext} will be skipped and {@link IndexSearcher} will |
| * swallow the exception and continue collection with the next leaf. |
| * |
| * <p>Note: This is called in an inner search loop. For good search performance, implementations |
| * of this method should not call {@link IndexSearcher#doc(int)} or {@link |
| * org.apache.lucene.index.IndexReader#document(int)} on every hit. Doing so can slow searches by |
| * an order of magnitude or more. |
| */ |
| void collect(int doc) throws IOException; |
| |
| /** |
| * Optionally returns an iterator over competitive documents. |
| * |
| * <p>Collectors should delegate this method to their comparators if their comparators provide the |
| * skipping functionality over non-competitive docs. |
| * |
| * <p>The default is to return {@code null} which is interpreted as the collector provide any |
| * competitive iterator. |
| */ |
| default DocIdSetIterator competitiveIterator() throws IOException { |
| return null; |
| } |
| } |