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Lucene example source code file (MergeDocIDRemapper.java)

This example Lucene source code file (MergeDocIDRemapper.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

mergedocidremapper, mergedocidremapper, segmentinfo, segmentinfo

The Lucene MergeDocIDRemapper.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.
 */

/** Remaps docIDs after a merge has completed, where the
 *  merged segments had at least one deletion.  This is used
 *  to renumber the buffered deletes in IndexWriter when a
 *  merge of segments with deletions commits. */

final class MergeDocIDRemapper {
  int[] starts;                                 // used for binary search of mapped docID
  int[] newStarts;                              // starts, minus the deletes
  int[][] docMaps;                              // maps docIDs in the merged set
  int minDocID;                                 // minimum docID that needs renumbering
  int maxDocID;                                 // 1+ the max docID that needs renumbering
  int docShift;                                 // total # deleted docs that were compacted by this merge

  public MergeDocIDRemapper(SegmentInfos infos, int[][] docMaps, int[] delCounts, MergePolicy.OneMerge merge, int mergedDocCount) {
    this.docMaps = docMaps;
    SegmentInfo firstSegment = merge.segments.get(0);
    int i = 0;
    while(true) {
      SegmentInfo info = infos.info(i);
      if (info.equals(firstSegment))
        break;
      minDocID += info.docCount;
      i++;
    }

    int numDocs = 0;
    for(int j=0;j<docMaps.length;i++,j++) {
      numDocs += infos.info(i).docCount;
      assert infos.info(i).equals(merge.segments.get(j));
    }
    maxDocID = minDocID + numDocs;

    starts = new int[docMaps.length];
    newStarts = new int[docMaps.length];

    starts[0] = minDocID;
    newStarts[0] = minDocID;
    for(i=1;i<docMaps.length;i++) {
      final int lastDocCount = merge.segments.get(i-1).docCount;
      starts[i] = starts[i-1] + lastDocCount;
      newStarts[i] = newStarts[i-1] + lastDocCount - delCounts[i-1];
    }
    docShift = numDocs - mergedDocCount;

    // There are rare cases when docShift is 0.  It happens
    // if you try to delete a docID that's out of bounds,
    // because the SegmentReader still allocates deletedDocs
    // and pretends it has deletions ... so we can't make
    // this assert here
    // assert docShift > 0;

    // Make sure it all adds up:
    assert docShift == maxDocID - (newStarts[docMaps.length-1] + merge.segments.get(docMaps.length-1).docCount - delCounts[docMaps.length-1]);
  }

  public int remap(int oldDocID) {
    if (oldDocID < minDocID)
      // Unaffected by merge
      return oldDocID;
    else if (oldDocID >= maxDocID)
      // This doc was "after" the merge, so simple shift
      return oldDocID - docShift;
    else {
      // Binary search to locate this document & find its new docID
      int lo = 0;                                      // search starts array
      int hi = docMaps.length - 1;                  // for first element less

      while (hi >= lo) {
        int mid = (lo + hi) >>> 1;
        int midValue = starts[mid];
        if (oldDocID < midValue)
          hi = mid - 1;
        else if (oldDocID > midValue)
          lo = mid + 1;
        else {                                      // found a match
          while (mid+1 < docMaps.length && starts[mid+1] == midValue) {
            mid++;                                  // scan to last match
          }
          if (docMaps[mid] != null)
            return newStarts[mid] + docMaps[mid][oldDocID-starts[mid]];
          else
            return newStarts[mid] + oldDocID-starts[mid];
        }
      }
      if (docMaps[hi] != null)
        return newStarts[hi] + docMaps[hi][oldDocID-starts[hi]];
      else
        return newStarts[hi] + oldDocID-starts[hi];
    }
  }
}

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