docs: private static TermvectorNumberBasic computeTermvectorNumberBasic(
        List<Integer> docSet, int termDocId, TermsEnum termsEnum, LeafReader r,
        LeafReaderContext lrc, PostingsEnum postingsEnum) throws IOException {
      TermvectorNumberBasic result = new TermvectorNumberBasic();
      boolean hasDeletedDocuments = (r.getLiveDocs() != null);
      if ((docSet.size() == r.numDocs()) && !hasDeletedDocuments) {
        try {
          return computeTermvectorNumberBasic(termsEnum, r);
        } catch (IOException e) {
          log.debug("problem", e);
          // problem
        }
      }
      result.docNumber = 0;
      result.valueSum[0] = 0;
      int localTermDocId = termDocId;
      Iterator<Integer> docIterator = docSet.iterator();
      postingsEnum = termsEnum.postings(postingsEnum, PostingsEnum.FREQS);
      int docId;
      while (docIterator.hasNext()) {
        docId = docIterator.next() - lrc.docBase;
        if (docId >= localTermDocId && ((docId == localTermDocId)
            || ((localTermDocId = postingsEnum.advance(docId)) == docId))) {
          result.docNumber++;
          result.valueSum[0] += postingsEnum.freq();
        }
        if (localTermDocId == DocIdSetIterator.NO_MORE_DOCS) {
          break;
        }
      }
      return result;
    }