pagination - swinton/django-rest-framework GitHub Wiki
Django provides a few classes that help you manage paginated data – that is, data that’s split across several pages, with “Previous/Next” links.
REST framework includes a PaginationSerializer
class that makes it easy to return paginated data in a way that can then be rendered to arbitrary media types.
Let's start by taking a look at an example from the Django documentation.
from django.core.paginator import Paginator
objects = ['john', 'paul', 'george', 'ringo']
paginator = Paginator(objects, 2)
page = paginator.page(1)
page.object_list
# ['john', 'paul']
At this point we've got a page object. If we wanted to return this page object as a JSON response, we'd need to provide the client with context such as next and previous links, so that it would be able to page through the remaining results.
from rest_framework.pagination import PaginationSerializer
serializer = PaginationSerializer(instance=page)
serializer.data
# {'count': 4, 'next': '?page=2', 'previous': None, 'results': [u'john', u'paul']}
The context
argument of the PaginationSerializer
class may optionally include the request. If the request is included in the context then the next and previous links returned by the serializer will use absolute URLs instead of relative URLs.
request = RequestFactory().get('/foobar')
serializer = PaginationSerializer(instance=page, context={'request': request})
serializer.data
# {'count': 4, 'next': 'http://testserver/foobar?page=2', 'previous': None, 'results': [u'john', u'paul']}
We could now return that data in a Response
object, and it would be rendered into the correct media type.
Our first example worked because we were using primitive objects. If we wanted to paginate a queryset or other complex data, we'd need to specify a serializer to use to serialize the result set itself.
We can do this using the object_serializer_class
attribute on the inner Meta
class of the pagination serializer. For example.
class UserSerializer(serializers.ModelSerializer):
"""
Serializes user querysets.
"""
class Meta:
model = User
fields = ('username', 'email')
class PaginatedUserSerializer(pagination.PaginationSerializer):
"""
Serializes page objects of user querysets.
"""
class Meta:
object_serializer_class = UserSerializer
We could now use our pagination serializer in a view like this.
@api_view('GET')
def user_list(request):
queryset = User.objects.all()
paginator = Paginator(queryset, 20)
page = request.QUERY_PARAMS.get('page')
try:
users = paginator.page(page)
except PageNotAnInteger:
# If page is not an integer, deliver first page.
users = paginator.page(1)
except EmptyPage:
# If page is out of range (e.g. 9999),
# deliver last page of results.
users = paginator.page(paginator.num_pages)
serializer_context = {'request': request}
serializer = PaginatedUserSerializer(users,
context=serializer_context)
return Response(serializer.data)
The generic class based views ListAPIView
and ListCreateAPIView
provide pagination of the returned querysets by default. You can customise this behaviour by altering the pagination style, by modifying the default number of results, by allowing clients to override the page size using a query parameter, or by turning pagination off completely.
The default pagination style may be set globally, using the DEFAULT_PAGINATION_SERIALIZER_CLASS
, PAGINATE_BY
, PAGINATE_BY_PARAM
, and MAX_PAGINATE_BY
settings. For example.
REST_FRAMEWORK = {
'PAGINATE_BY': 10, # Default to 10
'PAGINATE_BY_PARAM': 'page_size', # Allow client to override, using `?page_size=xxx`.
'MAX_PAGINATE_BY': 100 # Maximum limit allowed when using `?page_size=xxx`.
}
You can also set the pagination style on a per-view basis, using the ListAPIView
generic class-based view.
class PaginatedListView(ListAPIView):
queryset = ExampleModel.objects.all()
serializer_class = ExampleModelSerializer
paginate_by = 10
paginate_by_param = 'page_size'
max_paginate_by = 100
Note that using a paginate_by
value of None
will turn off pagination for the view.
Note if you use the PAGINATE_BY_PARAM
settings, you also have to set the paginate_by_param
attribute in your view to None
in order to turn off pagination for those requests that contain the paginate_by_param
parameter.
For more complex requirements such as serialization that differs depending on the requested media type you can override the .get_paginate_by()
and .get_pagination_serializer_class()
methods.
To create a custom pagination serializer class you should override pagination.BasePaginationSerializer
and set the fields that you want the serializer to return.
You can also override the name used for the object list field, by setting the results_field
attribute, which defaults to 'results'
.
For example, to nest a pair of links labelled 'prev' and 'next', and set the name for the results field to 'objects', you might use something like this.
from rest_framework import pagination
from rest_framework import serializers
class LinksSerializer(serializers.Serializer):
next = pagination.NextPageField(source='*')
prev = pagination.PreviousPageField(source='*')
class CustomPaginationSerializer(pagination.BasePaginationSerializer):
links = LinksSerializer(source='*') # Takes the page object as the source
total_results = serializers.Field(source='paginator.count')
results_field = 'objects'
To have your custom pagination serializer be used by default, use the DEFAULT_PAGINATION_SERIALIZER_CLASS
setting:
REST_FRAMEWORK = {
'DEFAULT_PAGINATION_SERIALIZER_CLASS':
'example_app.pagination.CustomPaginationSerializer',
}
Alternatively, to set your custom pagination serializer on a per-view basis, use the pagination_serializer_class
attribute on a generic class based view:
class PaginatedListView(generics.ListAPIView):
model = ExampleModel
pagination_serializer_class = CustomPaginationSerializer
paginate_by = 10
The following third party packages are also available.
The DRF-extensions
package includes a PaginateByMaxMixin
mixin class that allows your API clients to specify ?page_size=max
to obtain the maximum allowed page size.