docs: private Index ensureIndexed(List<FieldSort> fieldNames,
                                  String indexName,
                                  IndexType indexType,
                                  Tokenizer tokenizer) throws QueryException {
          // synchronized to prevent race conditions in IndexCreator when looking for existing indexes
          // which have the same name or definition
          synchronized (this) {
              return IndexCreator.ensureIndexed(new Index(fieldNames,
                              indexName,
                              indexType,
                              tokenizer),
                      database,
                      dbQueue);
          }
      }