| /* |
| * 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.index; |
| |
| |
| import java.io.Closeable; |
| import java.io.IOException; |
| |
| import org.apache.lucene.index.MergePolicy.OneMerge; |
| import org.apache.lucene.store.Directory; |
| import org.apache.lucene.store.RateLimitedIndexOutput; |
| import org.apache.lucene.util.InfoStream; |
| |
| /** <p>Expert: {@link IndexWriter} uses an instance |
| * implementing this interface to execute the merges |
| * selected by a {@link MergePolicy}. The default |
| * MergeScheduler is {@link ConcurrentMergeScheduler}.</p> |
| * @lucene.experimental |
| */ |
| public abstract class MergeScheduler implements Closeable { |
| |
| /** Sole constructor. (For invocation by subclass |
| * constructors, typically implicit.) */ |
| protected MergeScheduler() { |
| } |
| |
| /** Run the merges provided by {@link MergeSource#getNextMerge()}. |
| * @param mergeSource the {@link IndexWriter} to obtain the merges from. |
| * @param trigger the {@link MergeTrigger} that caused this merge to happen */ |
| public abstract void merge(MergeSource mergeSource, MergeTrigger trigger) throws IOException; |
| |
| /** |
| * Wraps the incoming {@link Directory} so that we can merge-throttle it |
| * using {@link RateLimitedIndexOutput}. |
| */ |
| public Directory wrapForMerge(OneMerge merge, Directory in) { |
| // A no-op by default. |
| return in; |
| } |
| |
| /** Close this MergeScheduler. */ |
| @Override |
| public abstract void close() throws IOException; |
| |
| /** For messages about merge scheduling */ |
| protected InfoStream infoStream; |
| |
| /** IndexWriter calls this on init. */ |
| void initialize(InfoStream infoStream, Directory directory) throws IOException { |
| this.infoStream = infoStream; |
| } |
| |
| /** |
| * Returns true if infoStream messages are enabled. This method is usually used in |
| * conjunction with {@link #message(String)}: |
| * |
| * <pre class="prettyprint"> |
| * if (verbose()) { |
| * message("your message"); |
| * } |
| * </pre> |
| */ |
| protected boolean verbose() { |
| return infoStream != null && infoStream.isEnabled("MS"); |
| } |
| |
| /** |
| * Outputs the given message - this method assumes {@link #verbose()} was |
| * called and returned true. |
| */ |
| protected void message(String message) { |
| infoStream.message("MS", message); |
| } |
| |
| /** |
| * Provides access to new merges and executes the actual merge |
| * @lucene.experimental |
| */ |
| public interface MergeSource { |
| /** |
| * The {@link MergeScheduler} calls this method to retrieve the next |
| * merge requested by the MergePolicy |
| */ |
| MergePolicy.OneMerge getNextMerge(); |
| |
| /** |
| * Does finishing for a merge. |
| */ |
| void onMergeFinished(MergePolicy.OneMerge merge); |
| |
| /** |
| * Expert: returns true if there are merges waiting to be scheduled. |
| */ |
| boolean hasPendingMerges(); |
| |
| /** |
| * Merges the indicated segments, replacing them in the stack with a |
| * single segment. |
| */ |
| void merge(MergePolicy.OneMerge merge) throws IOException; |
| } |
| } |