docs: private void buildTree(int left, int right, int axis, SortDBIDsBySingleDimension comp) {
      int middle = (left + right) >>> 1;
      comp.setDimension(axis);
      QuickSelectDBIDs.quickSelect(sorted, comp, left, right, middle);
  
      final int next = (axis + 1) % dims;
      if(left + leafsize < middle) {
        buildTree(left, middle, next, comp);
      }
      ++middle;
      if(middle + leafsize < right) {
        buildTree(middle, right, next, comp);
      }
    }