code: public ForeignSegmentDocId createDocId(String uuid) throws IOException {
          Term id = new Term(FieldNames.UUID,uuid);
          int doc;
          long tick;
          for (int i = 0; i < subReaders.length; i++) {
              TermDocs docs = subReaders[i].termDocs(id);
              try {
                  if (docs.next()) {
                      doc = docs.doc();
                      tick = subReaders[i].getCreationTick();
                      return new ForeignSegmentDocId(doc, tick);
                  }
              } finally {
                  docs.close();
              }
          }
          return null;
      }
docs: {@inheritDoc}