docs: public synchronized void close() throws Exception {
          if (!initialized) {
              throw new IllegalStateException("not initialized");
          }
  
          try {
              if (nameIndex instanceof DbNameIndex) {
                  ((DbNameIndex) nameIndex).close();
              }            
              // close blob store
              blobStore.close();
              blobStore = null;
              super.close();
          } finally {
              initialized = false;
          }
      }