Is Hibernate supposed to send SELECT for children collection of fetched parent while being marked with FetchType.Lazy?

I'm trying to understand how FetchType.Lazy works with Hibernate and I'm scratching my head...

I have an Order entity like so:

@Entity
@Table(name = "customer_order")
public class Order {

@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@OneToOne(cascade = CascadeType.ALL)
private Cart cart;
// unidirectional association

... other stuff omitted for brevity ...

And Cart Entity:

@Entity
@Table(name = "cart")
public class Cart {

@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

 ... some stuff omitted for brevity ...

@JsonManagedReference
@OneToMany(mappedBy = "cart", cascade = CascadeType.ALL, orphanRemoval = true)
private List<OrderItem> orderItems = new ArrayList<>();

public void addItem(OrderItem item) {
	orderItems.add(item);
	item.setCart(this);
}

public void removeItem(OrderItem item) {
	orderItems.remove(item);
	item.setCart(null);
}

And finally OrderItem:

Entity
@Table(name = "order_item")
public class OrderItem {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private Long id;

... fields omitted for brevity ...

@JsonBackReference
@ManyToOne(fetch = FetchType.LAZY)
private Cart cart;

@Override
public int hashCode() {
	return getClass().hashCode();
}

@Override
public boolean equals(Object obj) {
	if (this == obj)
		return true;

	if (!(obj instanceof OrderItem))
		return false;

	return id != null && id.equals(((OrderItem) obj).getId());
}

I have a controller -> serviceimpl -> repositoryimpl and I fetch an order like so:

@Override
public Order findById(Long id) {
	System.out.println(em.find(Order.class, id)); // to check what's fetched in memory
	return em.find(Order.class, id);
}

Hibernate generates the following:

Hibernate: 
select
    o1_0.id,
    a1_0.id,
    a1_0.door,
    a1_0.floor,
    a1_0.gate,
    a1_0.staircase,
    a1_0.street,
    a1_0.street_nr,
    c1_0.id,
    c1_0.total_cost,
    c1_0.total_cost_offers,
    c1_0.total_quantity,
    o1_0.contact_tel,
    o1_0.created_on,
    o1_0.c_first_name,
    o1_0.c_last_name,
    e1_0.id,
    e1_0.email,
    o2_0.id,
    o2_0.change_requested,
    o2_0.delivery_comment,
    o2_0.delivery_hour,
    o2_0.payment_change,
    o2_0.payment_type,
    o1_0.updated_on,
    o1_0.user_id 
from
    customer_order o1_0 
left join
    address a1_0 
        on a1_0.id=o1_0.address_id 
left join
    cart c1_0 
        on c1_0.id=o1_0.cart_id 
left join
    email e1_0 
        on e1_0.id=o1_0.email_id 
left join
    order_details o2_0 
        on o2_0.id=o1_0.order_details_id 
where
    o1_0.id=?
--- Should this following SELECT happen? Is it intended behavior since OneToMany default fetchType is LAZY?
Hibernate: 
select
    o1_0.cart_id,
    o1_0.id,
    o1_0.format,
    o1_0.name,
    o1_0.price,
    o1_0.product_type,
    o1_0.quantity 
from
    order_item o1_0 
where
    o1_0.cart_id=?

The output of cart obj in Postman is:

"cart": {
    "id": 3,
    "totalQuantity": 2,
    "totalCost": 29.5,
    "totalCostOffers": null,
    "orderItems": [
        {
            "id": 5,
            "productType": "pizza",
            "name": "Carbonara",
            "format": "M",
            "quantity": 1,
            "price": 14.75
        },
        {
            "id": 6,
            "productType": "pizza",
            "name": "Trufa Gurmet",
            "format": "M",
            "quantity": 1,
            "price": 14.75
        }
    ]
},

By the understanding I have of FetchType.LAZY, shouldn't the SELECT of OrderItems only happen if I do:

order.getCart().getOrderItems()

because OneToMany is FetchType.LAZY by default?

And until then the JSON ouput should be:

"cart": {
    "id": 3,
    "totalQuantity": 2,
    "totalCost": 29.5,
    "totalCostOffers": null,
},

If a cart would have a lot of order items children, how can they be "lazy" loaded/fetched so that the GET request would be efficient/not heavy? And then only load the cart items on demand (with another GET for example). Or the functionality I'm describing has to do with DTO projections and not FetchType.LAZY and I'm confusing the two?

Thanks!

So looking through the list of previously related questions asked I found something similar, but not quite the same thing that lead me to find the culprit of the additional SELECT statement:

In Cart Entity I had the auto-generated toString() include orderItems

    @Override
public String toString() {
return "Cart [id=" + id + ", totalQuantity=" + totalQuantity + ", totalCost=" + totalCost +     ", totalCostOffers="
			+ totalCostOffers + ", orderItems=" + orderItems + "]";
}

I removed + ", orderItems=" + orderItems and now Hibernate generates:

Hibernate: 
select
    o1_0.id,
    a1_0.id,
    a1_0.door,
    a1_0.floor,
    a1_0.gate,
    a1_0.staircase,
    a1_0.street,
    a1_0.street_nr,
    c1_0.id,
    c1_0.total_cost,
    c1_0.total_cost_offers,
    c1_0.total_quantity,
    o1_0.contact_tel,
    o1_0.created_on,
    o1_0.c_first_name,
    o1_0.c_last_name,
    e1_0.id,
    e1_0.email,
    o2_0.id,
    o2_0.change_requested,
    o2_0.delivery_comment,
    o2_0.delivery_hour,
    o2_0.payment_change,
    o2_0.payment_type,
    o1_0.updated_on,
    o1_0.user_id 
from
    customer_order o1_0 
left join
    address a1_0 
        on a1_0.id=o1_0.address_id 
join
    cart c1_0 
        on c1_0.id=o1_0.cart_id 
left join
    email e1_0 
        on e1_0.id=o1_0.email_id 
left join
    order_details o2_0 
        on o2_0.id=o1_0.order_details_id 
where
    o1_0.id=?

and the JSON output is:

"cart": {
    "id": 3,
    "totalQuantity": 2,
    "totalCost": 29.5,
    "totalCostOffers": null,
    "orderItems": null
},

I still posted the question and now I'm adding the answer so maybe it's helpful to others!

Original answer that helped me was:

https://stackoverflow.com/questions/32723627/when-query-to-parent-child-also-being-fetched-hibernate