Review

SegmentInfos.info(0) is called without prior check that there is at least one element in the SegmentInfos instance.

• missing/condition/value_or_state

org/apache/lucene/index/MergeDocIDRemapper.java

MergeDocIDRemapper(SegmentInfos, int[][], int[], OneMerge, int)

class MergeDocIDRemapper {
  public MergeDocIDRemapper(SegmentInfos infos, int[][] docMaps, int[] delCounts, MergePolicy.OneMerge merge, int mergedDocCount) {
    this.docMaps = docMaps;
    SegmentInfo firstSegment = merge.segments.info(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.info(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.info(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.info(docMaps.length-1).docCount - delCounts[docMaps.length-1]);
  }

}