| /* |
| * 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; |
| |
| /** |
| * <p>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> |
| * |
| * <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:</p> |
| * |
| * <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.</p> |
| * |
| * @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. |
| * |
| * Collectors should delegate this method to their comparators if |
| * their comparators provide the skipping functionality over non-competitive docs. |
| * |
| * The default is to return {@code null} which is interpreted as the collector provide any competitive iterator. |
| */ |
| default DocIdSetIterator competitiveIterator() throws IOException { |
| return null; |
| } |
| |
| } |