The Problem With Arrays for Pizza Toppings

Eric Normand: The problem with using arrays for pizza toppings is that you can have more than the limit. If I add mushrooms and then olives to an array, is that really a different pizza from olives mushroom? It's not that the data model maps to something that's not possible. That doesn't make sense. It's that it maps to encodings of the same thing. And that becomes a big problem when you start to ask questions like how many pizzas had mushrooms and olives?"