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使用Django REST Framework序列化程序进行高效连接

2017-06-20 54 views
0

我使用下面的一组序列化程序来实现连接，该连接在我的开发设置中工作正常，但在网站服务器和数据库服务器之间有任何距离时表现非常糟糕。我对运行这个节目的SQL有些怀疑，并做了一些日志记录;它似乎正在为每个条目做一个新的查询并合并结果，而不是一次完成整个连接并按照我的要求返回连接。这里是我的串行：使用Django REST Framework序列化程序进行高效连接

class UserSerializer(serializers.ModelSerializer): 
    class Meta: 
     model = User 
     exclude = ('password', 'last_login', 'is_superuser', 'is_staff', 'is_active', 'date_joined', 
        'groups', 'user_permissions') 


class DepartmentSerializer(serializers.HyperlinkedModelSerializer): 
    curator = UserSerializer() 
    class Meta: 
     model = Department 
     fields = '__all__' 


class CategorySerializer(serializers.HyperlinkedModelSerializer): 
    class Meta: 
     model = Category 
     fields = '__all__' 


class DetailedLinkedContentSerializer(serializers.HyperlinkedModelSerializer): 
    category = CategorySerializer() 
    department = DepartmentSerializer() 
    type = serializers.SerializerMethodField() 

    class Meta: 
     fields = '__all__' 
     model = LinkedContent 

    def get_type(self, obj): 
     return 'link' 


class DetailedFileContentSerializer(serializers.HyperlinkedModelSerializer): 
    category = CategorySerializer() 
    department = DepartmentSerializer() 
    link_url = serializers.SerializerMethodField() 
    type = serializers.SerializerMethodField() 

    class Meta: 
     fields = '__all__' 
     model = FileContent 

    def get_link_url(self, obj): 
     return obj.file.url 

    def get_type(self, obj): 
     return obj.file_type

正如你所看到的，我做我的，包括串行领域其他车型的序列化，如类= CategorySerializer（）“加入”。它看起来像DRF recommends，除非我误解了一些东西。这里是成百上千查询的一个小样本正在对我的开发环境中运行：

(0.001) SELECT "content_linkedcontent"."id", "content_linkedcontent"."link_text", "content_linkedcontent"."department_id", "content_linkedcontent"."category_id", "content_linkedcontent"."visibility_rank", "content_linkedcontent"."link_url" FROM "content_linkedcontent"; args=() 
(0.001) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 3; args=(3,) 
(0.001) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 24; args=(24,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 3; args=(3,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 3; args=(3,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 29; args=(29,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 4; args=(4,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 25; args=(25,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 1; args=(1,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 29; args=(29,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 1; args=(1,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 25; args=(25,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 1; args=(1,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 24; args=(24,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 3; args=(3,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 3; args=(3,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 28; args=(28,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 1; args=(1,) 
(0.000) SELECT "content_department"."id", "content_department"."name", "content_department"."description", "content_department"."curator_id", "content_department"."visibility_rank" FROM "content_department" WHERE "content_department"."id" = 28; args=(28,) 
(0.000) SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."id" = 6; args=(6,) 
(0.000) SELECT "content_category"."id", "content_category"."name", "content_category"."description" FROM "content_category" WHERE "content_category"."id" = 4; args=(4,)

那么，如何做一个真正的与我想在DRF使用串行信息加入？

UPDATE：

我有管理由以下的this博客条目的建议削减一半查询的时候，这里是使用他们我的更新序列化和视图：

class DetailedLinkedContentSerializer(serializers.HyperlinkedModelSerializer): 
    category = CategorySerializer() 
    department_query = Department.objects.all() 
    department_query = DepartmentSerializer.setup_eager_loading(department_query) 
    department = DepartmentSerializer(department_query) 
    # department = DepartmentSerializer() 
    type = serializers.SerializerMethodField() 

    class Meta: 
     fields = '__all__' 
     model = LinkedContent 

    def get_type(self, obj): 
     return 'link' 

    @staticmethod 
    def setup_eager_loading(queryset): 
     """ Perform necessary eager loading of data. """ 
     queryset = queryset.select_related('category', 'department') 
     return queryset 


class DetailedFileContentSerializer(serializers.HyperlinkedModelSerializer): 
    category = CategorySerializer() 
    department_query = Department.objects.all() 
    department_query = DepartmentSerializer.setup_eager_loading(department_query) 
    department = DepartmentSerializer(department_query) 
    # department = DepartmentSerializer() 
    link_url = serializers.SerializerMethodField() 
    type = serializers.SerializerMethodField() 

    class Meta: 
     fields = '__all__' 
     model = FileContent 

    def get_link_url(self, obj): 
     return obj.file.url 

    def get_type(self, obj): 
     return obj.file_type 

    @staticmethod 
    def setup_eager_loading(queryset): 
     """ Perform necessary eager loading of data. """ 
     queryset = queryset.select_related('category', 'department') 
     return queryset

和我查看使用这些序列化程序：

class DetailedContentView(views.APIView): 
    permission_classes = [IsAuthenticated, ContentCuratorOrReadOnly, IsGroupMember, ] 
    def get(self, request, *args, **kwargs): 
     context = {"request": request} 
     linked_content = LinkedContent.objects.all() 
     file_content = FileContent.objects.all() 
     # this line is newly added 
     linked_content = DetailedLinkedContentSerializer.setup_eager_loading(linked_content) 
     # this line too 
     file_content = DetailedLinkedContentSerializer.setup_eager_loading(file_content) 
     linked_content_serializer = DetailedLinkedContentSerializer(linked_content, many=True, context=context) 
     file_content_serializer = DetailedFileContentSerializer(file_content, many=True, context=context) 

     response = linked_content_serializer.data + file_content_serializer.data 
     response = sorted(response, key=lambda x: (x['department']['visibility_rank'], x['visibility_rank'])) 

     return Response(response)

但是，我的解决方案预取我的部门序列化程序中的用户序列化程序似乎并没有做的伎俩。具体来说，更新我的部门序列化后：

class DepartmentSerializer(serializers.HyperlinkedModelSerializer): 
    curator = UserSerializer() 
    class Meta: 
     model = Department 
     fields = '__all__' 

    @staticmethod 
    def setup_eager_loading(queryset): 
     """ Perform necessary eager loading of data. """ 
     queryset = queryset.select_related('curator') 
     return queryset

下面几行：

department_query = Department.objects.all() 
department_query = DepartmentSerializer.setup_eager_loading(department_query) 
department = DepartmentSerializer(department_query)

似乎并没有被预取我的策展人，因为我想要的。

来源

2017-06-20 DragonBobZ

+0

您是否尝试过使用[select_related]（https://docs.djangoproject.com/en/1.11/ref/models/querysets/#select-related）或[prefetch_related]（https://docs.djangoproject.com /en/1.11/ref/models/querysets/#prefetch-related）在您的视图中的查询集？这些应该预加载数据，避免每个条目和每个关系的新请求。 –

+0

我现在正在处理这个问题，而且我即将更新我的问题。 – DragonBobZ

回答

0

我使用一个混合从this blog发现评论更新我的串行：

class EagerLoadingMixin: 
    @classmethod 
    def setup_eager_loading(cls, queryset): 
     if hasattr(cls, "_SELECT_RELATED_FIELDS"): 
      queryset = queryset.select_related(*cls._SELECT_RELATED_FIELDS) 
     if hasattr(cls, "_PREFETCH_RELATED_FIELDS"): 
      queryset = queryset.prefetch_related(*cls._PREFETCH_RELATED_FIELDS) 
     return queryset

，并添加'department__curator'到我的预取字段列表。现在看起来像这样：

class DetailedFileContentSerializer(EagerLoadingMixin, serializers.HyperlinkedModelSerializer): 
    category = CategorySerializer() 
    department = DepartmentSerializer() 
    link_url = serializers.SerializerMethodField() 
    type = serializers.SerializerMethodField() 

    class Meta: 
     fields = '__all__' 
     model = FileContent 

    def get_link_url(self, obj): 
     return obj.file.url 

    def get_type(self, obj): 
     return obj.file_type 

    _SELECT_RELATED_FIELDS = ['department', 'category', 'department__curator']

该查询现在大约需要1/3的时间并且不包含数百个SELECT。它仍然需要很长时间，但我相信我可以通过更改切换到我的数据库的其他托管解决方案来解决这个问题。

来源

2017-06-20 23:22:12 DragonBobZ

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