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Lucene example source code file (UpgradeIndexMergePolicy.java)

This example Lucene source code file (UpgradeIndexMergePolicy.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

arraylist, corruptindexexception, corruptindexexception, io, ioexception, ioexception, map, mergepolicy, mergespecification, mergespecification, onemerge, override, override, segmentinfo, upgradeindexmergepolicy, util

The Lucene UpgradeIndexMergePolicy.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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import org.apache.lucene.util.Constants;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.HashMap;

/** This {@link MergePolicy} is used for upgrading all existing segments of
  * an index when calling {@link IndexWriter#optimize()}.
  * All other methods delegate to the base {@code MergePolicy} given to the constructor.
  * This allows for an as-cheap-as possible upgrade of an older index by only upgrading segments that
  * are created by previous Lucene versions. Optimize does no longer really optimize
  * it is just used to "optimize" older segment versions away.
  * <p>In general one would use {@link IndexUpgrader}, but for a fully customizeable upgrade,
  * you can use this like any other {@code MergePolicy} and call {@link IndexWriter#optimize()}:
  * <pre class="prettyprint lang-java">
  *  IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_XX, new KeywordAnalyzer());
  *  iwc.setMergePolicy(new UpgradeIndexMergePolicy(iwc.getMergePolicy()));
  *  IndexWriter w = new IndexWriter(dir, iwc);
  *  w.optimize();
  *  w.close();
  * </pre>
  * <p>Warning: This merge policy may reorder documents if the index was partially
  * upgraded before calling optimize (e.g., documents were added). If your application relies
  * on "monotonicity" of doc IDs (which means that the order in which the documents
  * were added to the index is preserved), do a full optimize instead. Please note, the
  * delegate {@code MergePolicy} may also reorder documents.
  * @lucene.experimental
  * @see IndexUpgrader
public class UpgradeIndexMergePolicy extends MergePolicy {

  protected final MergePolicy base;

  /** Wrap the given {@link MergePolicy} and intercept optimize requests to
   * only upgrade segments written with previous Lucene versions. */
  public UpgradeIndexMergePolicy(MergePolicy base) {
    this.base = base;
  /** Returns if the given segment should be upgraded. The default implementation
   * will return {@code !Constants.LUCENE_MAIN_VERSION.equals(si.getVersion())},
   * so all segments created with a different version number than this Lucene version will
   * get upgraded.
  protected boolean shouldUpgradeSegment(SegmentInfo si) {
    return !Constants.LUCENE_MAIN_VERSION.equals(si.getVersion());

  public void setIndexWriter(IndexWriter writer) {
  public MergeSpecification findMerges(SegmentInfos segmentInfos) throws CorruptIndexException, IOException {
    return base.findMerges(segmentInfos);
  public MergeSpecification findMergesForOptimize(SegmentInfos segmentInfos, int maxSegmentCount, Map<SegmentInfo,Boolean> segmentsToOptimize) throws CorruptIndexException, IOException {
    // first find all old segments
    final Map<SegmentInfo,Boolean> oldSegments = new HashMap();
    for (final SegmentInfo si : segmentInfos) {
      final Boolean v =segmentsToOptimize.get(si);
      if (v != null && shouldUpgradeSegment(si)) {
        oldSegments.put(si, v);
    if (verbose()) message("findMergesForOptimize: segmentsToUpgrade=" + oldSegments);
    if (oldSegments.isEmpty())
      return null;

    MergeSpecification spec = base.findMergesForOptimize(segmentInfos, maxSegmentCount, oldSegments);
    if (spec != null) {
      // remove all segments that are in merge specification from oldSegments,
      // the resulting set contains all segments that are left over
      // and will be merged to one additional segment:
      for (final OneMerge om : spec.merges) {

    if (!oldSegments.isEmpty()) {
      if (verbose())
        message("findMergesForOptimize: " +  base.getClass().getSimpleName() +
        " does not want to merge all old segments, merge remaining ones into new segment: " + oldSegments);
      final List<SegmentInfo> newInfos = new ArrayList();
      for (final SegmentInfo si : segmentInfos) {
        if (oldSegments.containsKey(si)) {
      // add the final merge
      if (spec == null) {
        spec = new MergeSpecification();
      spec.add(new OneMerge(newInfos));

    return spec;
  public MergeSpecification findMergesToExpungeDeletes(SegmentInfos segmentInfos) throws CorruptIndexException, IOException {
    return base.findMergesToExpungeDeletes(segmentInfos);
  public boolean useCompoundFile(SegmentInfos segments, SegmentInfo newSegment) throws IOException {
    return base.useCompoundFile(segments, newSegment);
  public void close() {
  public String toString() {
    return "[" + getClass().getSimpleName() + "->" + base + "]";
  private boolean verbose() {
    IndexWriter w = writer.get();
    return w != null && w.verbose();

  private void message(String message) {
    if (verbose())
      writer.get().message("UPGMP: " + message);

Other Lucene examples (source code examples)

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