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Diffstat (limited to 'src/core/Index/IndexDeletionPolicy.cs')
| -rw-r--r-- | src/core/Index/IndexDeletionPolicy.cs | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/src/core/Index/IndexDeletionPolicy.cs b/src/core/Index/IndexDeletionPolicy.cs new file mode 100644 index 0000000..bef9924 --- /dev/null +++ b/src/core/Index/IndexDeletionPolicy.cs @@ -0,0 +1,99 @@ +/* + * 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. + */ + +using System; +using System.Collections.Generic; + +namespace Lucene.Net.Index +{ + + /// <summary> <p/>Expert: policy for deletion of stale <see cref="IndexCommit">index commits</see>. + /// + /// <p/>Implement this interface, and pass it to one + /// of the <see cref="IndexWriter" /> or <see cref="IndexReader" /> + /// constructors, to customize when older + /// <see cref="IndexCommit">point-in-time commits</see> + /// are deleted from the index directory. The default deletion policy + /// is <see cref="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 <see cref="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/> + /// </summary> + + public interface IndexDeletionPolicy + { + + /// <summary> <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 <see cref="IndexCommit.Delete()" /> + /// of <see cref="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. + /// + /// </summary> + /// <param name="commits">List of current + /// <see cref="IndexCommit">point-in-time commits</see>, + /// sorted by age (the 0th one is the oldest commit). + /// </param> + void OnInit<T>(IList<T> commits) where T : IndexCommit; + + /// <summary> + /// <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 <see cref="IndexCommit.Delete()"/> + /// of <see cref="IndexCommit" />.</p> + /// + /// <p>This method is only called when <see cref="IndexWriter.Commit()"/> + /// or <see cref="IndexWriter.Close()"/> is called, or possibly not at + /// all if the <see cref="IndexWriter.Rollback()"/> is called.</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.</p> + /// </summary> + /// <param name="commits"> + /// List of <see cref="IndexCommit" />, sorted by age (the 0th one is the oldest commit). + /// </param> + void OnCommit<T>(IList<T> commits) where T : IndexCommit; + } +}
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