Django REST Framework에서 복잡한 JSON 응답을 효율적으로 다루기 SerializerMethodField부터 JsonField와 JSONObject까지

class Order(models.Model):
			...(주문에 관한 정보)

class OrderItem(models.Model):
    order = models.ForeignKey(Order, related_name='items', on_delete=models.CASCADE)
    product =  models.ForeignKey(Product, related_name='product_order_items',...)
    quantity = models.IntegerField(...)
    price = models.DecimalField(...)
    ...

class OrderSerializer(serializers.ModelSerializer):
    total_amount = SerializerMethodField()
    items = SerializerMethodField()

    def get_total_amount(self, obj):
        return obj.total

    def get_items(self, obj):
        return [{
            'id': item.id,
            'name': item.product.name,
            'quantity': item.quantity
        } for item in obj.items.all()]

class OrderViewSet(viewsets.ModelViewSet):
    def get_queryset(self):
        return Order.objects.annotate(
            total=Sum(F('items__price') * F('items__quantity'))
        ).select_related('customer').prefetch_related(
            Prefetch(
                'items',
                queryset=OrderItem.objects.select_related('product'),
                to_attr='prefetched_items'  # 캐싱을 위한 속성 지정
            )
        )

class OrderSerializer(serializers.ModelSerializer):
    items = SerializerMethodField()

    def get_items(self, obj):
        # prefetched_items 활용
        items = getattr(obj, 'prefetched_items', obj.items.all())
        return [{
            'id': item.id,
            'name': item.product.name,
            'quantity': item.quantity
        } for item in items]

class OrderItemSerializer(ModelSerializer):
    class Meta:
        model = OrderItem
        fields = ['id', 'product', 'quantity', 'price']

class OrderSerializer(ModelSerializer):
    items = OrderItemSerializer(many=True)

    class Meta:
        model = Order
        fields = ['id', 'total_amount', 'items']

class OrderViewSet(viewsets.ModelViewSet):
    serializer_class = OrderSerializer

    def get_queryset(self):
        return Order.objects.annotate(
            total_amount=Sum(F('items__price') * F('items__quantity')),
            items=JSONObject(
                id=F('items__id'),
                name=F('items__product__name'),
                quantity=F('items__quantity')
            )
        )

class OrderSerializer(serializers.ModelSerializer):
    class Meta:
        model = Order
        fields = ['id', 'total_amount', 'items']

class OrderItem(models.Model):
		...
    options = models.JSONField(default=dict)  # 상품 옵션 정보
    shipping_info = models.JSONField(default=dict)  # 배송 관련 정보

# options 예시
{
    "size": "XL",
    "color": "Navy",
    "material": "Cotton"
}

# shipping_info 예시
{
    "method": "express",
    "tracking_number": "1234567890",
    "estimated_delivery": "2024-01-30",
    "special_instructions": "부재시 경비실"
}

...
from django.db.models.functions import ExtractValue
from django.db.models.functions.json import KeyTextTransform

class OrderViewSet(viewsets.ModelViewSet):
    def get_queryset(self):
# shipping_method로 필터링
        queryset = OrderItem.objects.annotate(
            shipping_method=KeyTextTransform('method', 'shipping_info')
        ).filter(shipping_method='express')

# size와 color를 기준으로 정렬
        queryset = queryset.annotate(
            option_size=KeyTextTransform('size', 'options'),
            option_color=KeyTextTransform('color', 'options')
        ).order_by('option_size', 'option_color')

        return queryset

"""예시
{
    "details": {
        "manufacturer": {
            "name": "Company A",
            "country": "Korea"
        }
    }
}

"""

queryset = OrderItem.objects.annotate(
    manufacturer_country=KeyTextTransform(
        'country',
        KeyTextTransform( # 중첩 가능
            'manufacturer',
            KeyTextTransform('details', 'options')
        )
    )
).filter(manufacturer_country='Korea')

OrderItem.objects.filter(id=1).update(
    options=JSONObject(
        size=F('options__size'),# 유지됨
        material=F('options__material'),# 유지됨
        color='Blue',# 새로운 값으로 업데이트
				...
    )
)

UPDATE "order_item"
SET "options" = jsonb_build_object(
    'size', "order_item"."options"->>'size',
    'color', 'Blue',
    'material', "order_item"."options"->>'material'
)
WHERE "order_item"."id" = 1;

@transaction.atomic
def bulk_update_json_field(queryset, updates):
    """
    효율적인 벌크 업데이트를 위한 함수

    :param queryset: 업데이트할 queryset
    :param updates: 업데이트할 내용을 별도로 입력하여 구분.
    """
    updated_count = queryset.update(
        options=JSONObject(
            **{
                'size': F('options__size'),
                'material': F('options__material'),
                **updates  # 새로운 값으로 업데이트할 필드
            }
        )
    )
    return updated_count

# 사용 예시
items_to_update = OrderItem.objects.filter(Q(options__color='Red'))
updates = {'color': 'Blue', 'updated_at': '2025-01-01'}
updated_count = bulk_update_json_field(items_to_update, updates)