| package org.apache.lucene.search; |
| |
| /** |
| * 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. |
| */ |
| |
| import java.io.IOException; |
| |
| /** |
| * A DocIdSet contains a set of doc ids. Implementing classes must |
| * only implement {@link #iterator} to provide access to the set. |
| */ |
| public abstract class DocIdSet { |
| |
| /** An empty {@code DocIdSet} instance for easy use, e.g. in Filters that hit no documents. */ |
| public static final DocIdSet EMPTY_DOCIDSET = new DocIdSet() { |
| |
| private final DocIdSetIterator iterator = new DocIdSetIterator() { |
| @Override |
| public int advance(int target) throws IOException { return NO_MORE_DOCS; } |
| @Override |
| public int docID() { return NO_MORE_DOCS; } |
| @Override |
| public int nextDoc() throws IOException { return NO_MORE_DOCS; } |
| }; |
| |
| @Override |
| public DocIdSetIterator iterator() { |
| return iterator; |
| } |
| |
| @Override |
| public boolean isCacheable() { |
| return true; |
| } |
| }; |
| |
| /** Provides a {@link DocIdSetIterator} to access the set. |
| * This implementation can return <code>null</code> or |
| * <code>{@linkplain #EMPTY_DOCIDSET}.iterator()</code> if there |
| * are no docs that match. */ |
| public abstract DocIdSetIterator iterator() throws IOException; |
| |
| /** |
| * This method is a hint for {@link CachingWrapperFilter}, if this <code>DocIdSet</code> |
| * should be cached without copying it into a BitSet. The default is to return |
| * <code>false</code>. If you have an own <code>DocIdSet</code> implementation |
| * that does its iteration very effective and fast without doing disk I/O, |
| * override this method and return <code>true</here>. |
| */ |
| public boolean isCacheable() { |
| return false; |
| } |
| } |