| /* |
| * 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.Collection; |
| |
| /** |
| * A manager of collectors. This class is useful to parallelize execution of |
| * search requests and has two main methods: |
| * <ul> |
| * <li>{@link #newCollector()} which must return a NEW collector which |
| * will be used to collect a certain set of leaves.</li> |
| * <li>{@link #reduce(Collection)} which will be used to reduce the |
| * results of individual collections into a meaningful result. |
| * This method is only called after all leaves have been fully |
| * collected.</li> |
| * </ul> |
| * |
| * @see IndexSearcher#search(Query, CollectorManager) |
| * @lucene.experimental |
| */ |
| public interface CollectorManager<C extends Collector, T> { |
| |
| /** |
| * Return a new {@link Collector}. This must return a different instance on |
| * each call. |
| */ |
| C newCollector() throws IOException; |
| |
| /** |
| * Reduce the results of individual collectors into a meaningful result. |
| * For instance a {@link TopDocsCollector} would compute the |
| * {@link TopDocsCollector#topDocs() top docs} of each collector and then |
| * merge them using {@link TopDocs#merge(int, TopDocs[])}. |
| * This method must be called after collection is finished on all provided |
| * collectors. |
| */ |
| T reduce(Collection<C> collectors) throws IOException; |
| |
| } |