Question

我正在访问SerializerMethodField中的相关字段数据，并且每个正在呈现的对象都有一个查询。我的模型看起来像（为了简洁起见）：

class Listing(models.Model):

variant = models.ForeignKey(to='Variant', related_name='variant_listings')
seller = models.ForeignKey(to='user.Seller', related_name='seller_listings')
locality = models.ForeignKey(to='user.Locality', blank=True, null=True)
price = models.IntegerField(blank=True, null=True)

Variant，Seller和Locality都是相关模型。

我的观点：

class ListingViewSet(viewsets.ModelViewSet):
    """Viewset class for Listing model"""

    queryset = Listing.objects.all()
    serializer_class = ListingSerializer
    pagination_class = TbPagination
    filter_backends = (filters.DjangoFilterBackend,)
    filter_class = ListingFilter

    def get_queryset(self):

        listing_qs = Listing.objects.filter(status='active')
        listing_qs = ListingSerializer.setup_eager_loading(listing_qs)
        return listing_qs

我的序列化器：

class ListingSerializer(serializers.ModelSerializer):
"""Serializer class for Listing model"""

@staticmethod
def setup_eager_loading(queryset):
    queryset = queryset.prefetch_related('variant', 'seller', 'locality')
    return queryset

@staticmethod
def get_car_link(obj):
    variant_name_slug = obj.variant.name.replace(' ', '-').replace('+', '')
    return '/buy-' + obj.seller.city.name.lower() + '/' + variant_name_slug

car_link = serializers.SerializerMethodField(read_only=True)

@staticmethod
def get_car_info(obj):
    return {
        'id': obj.id,
        'variant_name': obj.variant.name,
        'localities': obj.locality.name,
    }

car_info = serializers.SerializerMethodField(read_only=True)

@staticmethod
def get_image_urls(obj):
    caption_ids = [1, 2, 3, 5, 7, 8, 18]
    attachments_qs = Attachment.objects.filter(listing_id=obj.id, caption_id__in=caption_ids)
    image_urls = []
    for attachment in attachments_qs:
        url = str(obj.id) + '-' + str(attachment.file_number) + '-360.jpg'
        image_urls.append(url)

    return image_urls

image_urls = serializers.SerializerMethodField(read_only=True)

class Meta:
    model = Listing
    fields = ('car_link', 'car_info', 'sort_by', 'image_urls')

对于列表视图集返回的每个列表，都会查询SerializerMethodField中访问的每个相关字段。

我找到了一些相关问题，例如this。但这没有帮助。另外，我尝试在视图集的get_queryset方法上执行prefetch_related，并在this文章的帮助下实现了预先加载。但没有任何帮助。

有没有办法避免这些疑问？

修改

上面写的get_car_info函数包含一些字段（以及已经存在的字段），这些字段在嵌套的JSON中需要通过前端渲染的最终序列化数据中的car_info名称单独使用。 / p>

Answer 1

我用过这篇文章： http://ses4j.github.io/2015/11/23/optimizing-slow-django-rest-framework-performance/

我在序列化程序中创建了一个设置急切加载方法，如下所示：

class EagerGetProjectSerializer(serializers.ModelSerializer):
    lead_researcher = UserSerializer()
    participating_researcher = UserSerializer(many=True)
    client = ProjectClientSerializer()
    test_items = TestItemSerializer(many=True)


    @staticmethod
    def setup_eager_loading(queryset):
        queryset = queryset.select_related('lead_researcher', 'client')
        queryset = queryset.prefetch_related('participating_researcher', 
        'test_items')
        return queryset


    class Meta:
        model = Project
        fields = '__all__'

请注意，在引用要拉入序列化程序的对象时，必须使用与外键相关的名称属性。

并在访问序列化程序之前在我看来调用：

class SingleProject(APIView):
    def get(self, request):
        ans = Project.objects.filter(id=project_id)
        qs = EagerGetProjectSerializer.setup_eager_loading(ans)
        serializer = EagerGetProjectSerializer(qs, many=True)

在Django REST框架

1 个答案: