If you've got a hierarchy with a depth of around 500 you can't rebuild! the tree without it resulting in a SystemStackError: stack level too deep.

Here's a test that illustrates the failure. I don't have a patch or workaround, but wanted to report it.

    it 'rebuilds deeply nested tree' do
      parent = nil
      500.times do |counter|
        parent = Metal.create(:value => "Nitro-#{counter}", parent: parent)
      end
      expect { Metal.rebuild! }.not_to raise_error
    end