Lucene example source code file (IndexCommit.java)

This example Lucene source code file (IndexCommit.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

collection, comparable, directory, indexcommit, indexcommit, io, ioexception, ioexception, map, map, override, override, string, util

The Lucene IndexCommit.java source code

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.Collection;
import java.util.Map;
import java.io.IOException;

import org.apache.lucene.store.Directory;

/**
 * <p>Expert: represents a single commit into an index as seen by the
 * {@link IndexDeletionPolicy} or {@link IndexReader}.</p>
 *
 * <p> Changes to the content of an index are made visible
 * only after the writer who made that change commits by
 * writing a new segments file
 * (<code>segments_N). This point in time, when the
 * action of writing of a new segments file to the directory
 * is completed, is an index commit.</p>
 *
 * <p>Each index commit point has a unique segments file
 * associated with it. The segments file associated with a
 * later index commit point would have a larger N.</p>
 *
 * @lucene.experimental
*/

public abstract class IndexCommit implements Comparable<IndexCommit> {

  /**
   * Get the segments file (<code>segments_N) associated 
   * with this commit point.
   */
  public abstract String getSegmentsFileName();

  /**
   * Returns all index files referenced by this commit point.
   */
  public abstract Collection<String> getFileNames() throws IOException;

  /**
   * Returns the {@link Directory} for the index.
   */
  public abstract Directory getDirectory();
  
  /**
   * Delete this commit point.  This only applies when using
   * the commit point in the context of IndexWriter's
   * IndexDeletionPolicy.
   * <p>
   * Upon calling this, the writer is notified that this commit 
   * point should be deleted. 
   * <p>
   * Decision that a commit-point should be deleted is taken by the {@link IndexDeletionPolicy} in effect
   * and therefore this should only be called by its {@link IndexDeletionPolicy#onInit onInit()} or 
   * {@link IndexDeletionPolicy#onCommit onCommit()} methods.
  */
  public abstract void delete();

  public abstract boolean isDeleted();

  /** Returns true if this commit is an optimized index. */
  public abstract boolean isOptimized();

  /** Two IndexCommits are equal if both their Directory and versions are equal. */
  @Override
  public boolean equals(Object other) {
    if (other instanceof IndexCommit) {
      IndexCommit otherCommit = (IndexCommit) other;
      return otherCommit.getDirectory().equals(getDirectory()) && otherCommit.getVersion() == getVersion();
    } else
      return false;
  }

  @Override
  public int hashCode() {
    return (int) (getDirectory().hashCode() + getVersion());
  }

  /** Returns the version for this IndexCommit.  This is the
   *  same value that {@link IndexReader#getVersion} would
   *  return if it were opened on this commit. */
  public abstract long getVersion();

  /** Returns the generation (the _N in segments_N) for this
   *  IndexCommit */
  public abstract long getGeneration();

  /** Convenience method that returns the last modified time
   *  of the segments_N file corresponding to this index
   *  commit, equivalent to
   *  getDirectory().fileModified(getSegmentsFileName()). */
  public long getTimestamp() throws IOException {
    return getDirectory().fileModified(getSegmentsFileName());
  }

  /** Returns userData, previously passed to {@link
   *  IndexWriter#commit(Map)} for this commit.  Map is
   *  String -> String. */
  public abstract Map<String,String> getUserData() throws IOException;
  
  public int compareTo(IndexCommit commit) {
    long gen = getGeneration();
    long comgen = commit.getGeneration();
    if (gen < comgen) {
      return -1;
    } else if (gen > comgen) {
      return 1;
    } else {
      return 0;
    }
  }

}