code: func (mp *LogMergePolicy) sizeDocs(info *SegmentCommitInfo, w *IndexWriter) (n int64, err error) {
  	infoDocCount := info.Info.DocCount()
  	if mp.calibrateSizeByDeletes {
  		delCount := w.readerPool.numDeletedDocs(info)
  		assert(delCount <= infoDocCount)
  		return int64(infoDocCount - delCount), nil
  	}
  	return int64(infoDocCount), nil
  }
docs: /*
  Return the number of documents in the provided SegmentCommitInfo,
  pro-rated by percentage of non-deleted documents if
  SetCalibrateSizeByDeletes() is set.
  */