| package org.apache.lucene.index; |
| |
| /* |
| * 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.util.List; |
| import java.io.IOException; |
| |
| /** |
| * <p>Expert: policy for deletion of stale {@link IndexCommit index commits}. |
| * |
| * <p>Implement this interface, and pass it to one |
| * of the {@link IndexWriter} or {@link IndexReader} |
| * constructors, to customize when older |
| * {@link IndexCommit point-in-time commits} |
| * are deleted from the index directory. The default deletion policy |
| * is {@link KeepOnlyLastCommitDeletionPolicy}, which always |
| * removes old commits as soon as a new commit is done (this |
| * matches the behavior before 2.2).</p> |
| * |
| * <p>One expected use case for this (and the reason why it |
| * was first created) is to work around problems with an |
| * index directory accessed via filesystems like NFS because |
| * NFS does not provide the "delete on last close" semantics |
| * that Lucene's "point in time" search normally relies on. |
| * By implementing a custom deletion policy, such as "a |
| * commit is only removed once it has been stale for more |
| * than X minutes", you can give your readers time to |
| * refresh to the new commit before {@link IndexWriter} |
| * removes the old commits. Note that doing so will |
| * increase the storage requirements of the index. See <a |
| * target="top" |
| * href="http://issues.apache.org/jira/browse/LUCENE-710">LUCENE-710</a> |
| * for details.</p> |
| */ |
| |
| public abstract class IndexDeletionPolicy implements Cloneable { |
| |
| /** Sole constructor, typically called by sub-classes constructors. */ |
| protected IndexDeletionPolicy() {} |
| |
| /** |
| * <p>This is called once when a writer is first |
| * instantiated to give the policy a chance to remove old |
| * commit points.</p> |
| * |
| * <p>The writer locates all index commits present in the |
| * index directory and calls this method. The policy may |
| * choose to delete some of the commit points, doing so by |
| * calling method {@link IndexCommit#delete delete()} |
| * of {@link IndexCommit}.</p> |
| * |
| * <p><u>Note:</u> the last CommitPoint is the most recent one, |
| * i.e. the "front index state". Be careful not to delete it, |
| * unless you know for sure what you are doing, and unless |
| * you can afford to lose the index content while doing that. |
| * |
| * @param commits List of current |
| * {@link IndexCommit point-in-time commits}, |
| * sorted by age (the 0th one is the oldest commit). |
| */ |
| public abstract void onInit(List<? extends IndexCommit> commits) throws IOException; |
| |
| /** |
| * <p>This is called each time the writer completed a commit. |
| * This gives the policy a chance to remove old commit points |
| * with each commit.</p> |
| * |
| * <p>The policy may now choose to delete old commit points |
| * by calling method {@link IndexCommit#delete delete()} |
| * of {@link IndexCommit}.</p> |
| * |
| * <p>This method is only called when {@link |
| * IndexWriter#commit} or {@link IndexWriter#close} is |
| * called, or possibly not at all if the {@link |
| * IndexWriter#rollback} is called. |
| * |
| * <p><u>Note:</u> the last CommitPoint is the most recent one, |
| * i.e. the "front index state". Be careful not to delete it, |
| * unless you know for sure what you are doing, and unless |
| * you can afford to lose the index content while doing that. |
| * |
| * @param commits List of {@link IndexCommit}, |
| * sorted by age (the 0th one is the oldest commit). |
| */ |
| public abstract void onCommit(List<? extends IndexCommit> commits) throws IOException; |
| |
| @Override |
| public IndexDeletionPolicy clone() { |
| try { |
| return (IndexDeletionPolicy) super.clone(); |
| } catch (CloneNotSupportedException e) { |
| throw new Error(e); |
| } |
| } |
| |
| } |