what's the use if I am querying all the database before pagination in Django? - django

Question

as per below code I am doing the query for database then I am paginating the query result. so My question what's the use if we already hit the database for all result before pagination. Is this like Django pagination working or I am pretending something wrong?
I am getting the response as expected but had question querying the database before pagination.
Code:
class GetAllUserStoryListViewTest(APIView,LimitOffsetPagination):
permission_classes = (IsAuthenticated,)
def get_object(self,user_id):
user = User.objects.filter(id = user_id).first()
posts = Post.objects.filter(user = user)
return posts
def get(self,request,user_id):
posts = self.get_object(user_id).order_by('-post_time_stamp')
#setting the limit of this user post pagination
LimitOffsetPagination.default_limit = settings.PAGE_SIZE
posts = self.paginate_queryset(posts, request)
serializer_context = {
'request': request,
}
serializer = PostListSerializer(posts,many=True,context=serializer_context)
# return Response(serializer.data)
return self.get_paginated_response(serializer.data)
output:
{
"count": 7,
"next": "http://127.0.0.1:8000/api/list_all_story_test/27/?limit=2&offset=5",
"previous": "http://127.0.0.1:8000/api/list_all_story_test/27/?limit=2&offset=1",
"results": [
{
"id": 15,
"file": "http://127.0.0.1:8000/media/user_27/post/IMG_20190331_144024.jpg",
"post_info": "#cool",
"post_time_stamp": "2020-05-10T10:21:10Z",
"total_comment": 2,
"liked_by": [
"vipin"
],
"user": {
"id": 27,
"username": "vipin",
"email": "vipinks#xyz.edu",
"status": true,
"profile": {
"id": 24,
"full_name": "Vipin",
"mobile": 6732,
"background_picture": "http://127.0.0.1:8000/media/user_27/profile/pexels-photo-531880_0qSgRNx.jpeg",
"profile_picture": "http://127.0.0.1:8000/media/user_27/profile/IMG_20190331_144024.jpg",
"BioDescription": "xyz",
"date_of_birth": "1996-06-01",
"gender": "M",
"account_type": "Private",
"user": 27
},
"last_login": null,
"is_superuser": false,
"is_staff": false,
"is_active": true,
"date_joined": "2020-04-28T11:09:27.691478Z"
},
"comment_usr": [
"xyz",
26,
"Cool Pic"
],
"like_by_you": true
},
{
"id": 13,
"file": "http://127.0.0.1:8000/media/user_30/post/IMG_20190402_102248.jpg",
"post_info": "#Awesome",
"post_time_stamp": "2020-05-10T10:20:22Z",
"total_comment": 8,
"user": {
"id": 30,
"username": "xyz",
"email": "xyz#gmail.com",
"status": false,
"profile": {
"id": 27,
"full_name": "XYZ",
"mobile": 123,
"background_picture": null,
"profile_picture": "http://127.0.0.1:8000/media/user_30/profile/demo.jpg",
"BioDescription": null,
"date_of_birth": null,
"gender": "F",
"account_type": "Private",
"user": 30
},
"last_login": null,
"is_superuser": false,
"is_staff": false,
"is_active": true,
"date_joined": "2020-04-28T11:13:58.030941Z"
},
"like_by_you": true
}
]
}

Answer 1

The pagination hit the database with Count() method, to paginating the result.
And, in every page hit the database by slicing that is more efficient than
using a queryset with all() method and, hit the database with Iteration, which load all the results.
filter() or all() methods don't hit the database. See this to check when a QuerySet is evaluated.