docs: @Override
    public void initializeFromFile(TreeIndexHeader header, PageFile<FlatRStarTreeNode> file) {
      super.initializeFromFile(header, file);
  
      // reconstruct root
      int nextPageID = file.getNextPageID();
      dirCapacity = nextPageID;
      root = createNewDirectoryNode();
      for(int i = 1; i < nextPageID; i++) {
        FlatRStarTreeNode node = getNode(i);
        root.addDirectoryEntry(createNewDirectoryEntry(node));
      }
  
      if(LOG.isDebugging()) {
        LOG.debugFine("root: " + root + " with " + nextPageID + " leafNodes.");
      }
    }