switch (range.getLowerBoundType()) {
        case OPEN:
          return aggr.nodeAggregate(node) + aggr.treeAggregate(node.left);
        case CLOSED:
          return aggr.treeAggregate(node.left);
      }
      throw new AssertionError();
    } else {
      return aggr.treeAggregate(node.left)
          + aggr.nodeAggregate(node)
          + aggregateBelowRange(aggr, node.right);
    }
  }