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https://github.com/encode/django-rest-framework.git
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726 lines
26 KiB
Python
726 lines
26 KiB
Python
# coding: utf-8
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"""
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Pagination serializers determine the structure of the output that should
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be used for paginated responses.
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"""
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from __future__ import unicode_literals
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from base64 import b64decode, b64encode
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from collections import OrderedDict, namedtuple
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from django.core.paginator import Paginator as DjangoPaginator
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from django.core.paginator import InvalidPage
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from django.template import loader
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from django.utils import six
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from django.utils.six.moves.urllib import parse as urlparse
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from django.utils.translation import ugettext_lazy as _
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from rest_framework.compat import template_render
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from rest_framework.exceptions import NotFound
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from rest_framework.response import Response
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from rest_framework.settings import api_settings
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from rest_framework.utils.urls import remove_query_param, replace_query_param
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def _positive_int(integer_string, strict=False, cutoff=None):
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"""
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Cast a string to a strictly positive integer.
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"""
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ret = int(integer_string)
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if ret < 0 or (ret == 0 and strict):
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raise ValueError()
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if cutoff:
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ret = min(ret, cutoff)
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return ret
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def _divide_with_ceil(a, b):
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"""
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Returns 'a' divided by 'b', with any remainder rounded up.
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"""
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if a % b:
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return (a // b) + 1
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return a // b
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def _get_count(queryset):
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"""
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Determine an object count, supporting either querysets or regular lists.
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"""
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try:
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return queryset.count()
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except (AttributeError, TypeError):
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return len(queryset)
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def _get_displayed_page_numbers(current, final):
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"""
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This utility function determines a list of page numbers to display.
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This gives us a nice contextually relevant set of page numbers.
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For example:
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current=14, final=16 -> [1, None, 13, 14, 15, 16]
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This implementation gives one page to each side of the cursor,
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or two pages to the side when the cursor is at the edge, then
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ensures that any breaks between non-continuous page numbers never
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remove only a single page.
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For an alternative implementation which gives two pages to each side of
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the cursor, eg. as in GitHub issue list pagination, see:
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https://gist.github.com/tomchristie/321140cebb1c4a558b15
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"""
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assert current >= 1
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assert final >= current
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if final <= 5:
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return list(range(1, final + 1))
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# We always include the first two pages, last two pages, and
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# two pages either side of the current page.
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included = {1, current - 1, current, current + 1, final}
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# If the break would only exclude a single page number then we
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# may as well include the page number instead of the break.
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if current <= 4:
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included.add(2)
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included.add(3)
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if current >= final - 3:
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included.add(final - 1)
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included.add(final - 2)
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# Now sort the page numbers and drop anything outside the limits.
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included = [
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idx for idx in sorted(list(included))
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if idx > 0 and idx <= final
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]
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# Finally insert any `...` breaks
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if current > 4:
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included.insert(1, None)
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if current < final - 3:
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included.insert(len(included) - 1, None)
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return included
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def _get_page_links(page_numbers, current, url_func):
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"""
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Given a list of page numbers and `None` page breaks,
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return a list of `PageLink` objects.
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"""
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page_links = []
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for page_number in page_numbers:
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if page_number is None:
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page_link = PAGE_BREAK
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else:
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page_link = PageLink(
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url=url_func(page_number),
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number=page_number,
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is_active=(page_number == current),
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is_break=False
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)
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page_links.append(page_link)
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return page_links
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def _reverse_ordering(ordering_tuple):
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"""
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Given an order_by tuple such as `('-created', 'uuid')` reverse the
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ordering and return a new tuple, eg. `('created', '-uuid')`.
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"""
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def invert(x):
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return x[1:] if (x.startswith('-')) else '-' + x
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return tuple([invert(item) for item in ordering_tuple])
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Cursor = namedtuple('Cursor', ['offset', 'reverse', 'position'])
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PageLink = namedtuple('PageLink', ['url', 'number', 'is_active', 'is_break'])
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PAGE_BREAK = PageLink(url=None, number=None, is_active=False, is_break=True)
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class BasePagination(object):
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display_page_controls = False
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def paginate_queryset(self, queryset, request, view=None): # pragma: no cover
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raise NotImplementedError('paginate_queryset() must be implemented.')
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def get_paginated_response(self, data): # pragma: no cover
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raise NotImplementedError('get_paginated_response() must be implemented.')
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def to_html(self): # pragma: no cover
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raise NotImplementedError('to_html() must be implemented to display page controls.')
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def get_results(self, data):
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return data['results']
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def get_fields(self, view):
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return []
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class PageNumberPagination(BasePagination):
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"""
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A simple page number based style that supports page numbers as
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query parameters. For example:
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http://api.example.org/accounts/?page=4
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http://api.example.org/accounts/?page=4&page_size=100
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"""
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# The default page size.
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# Defaults to `None`, meaning pagination is disabled.
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page_size = api_settings.PAGE_SIZE
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django_paginator_class = DjangoPaginator
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# Client can control the page using this query parameter.
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page_query_param = 'page'
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# Client can control the page size using this query parameter.
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# Default is 'None'. Set to eg 'page_size' to enable usage.
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page_size_query_param = None
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# Set to an integer to limit the maximum page size the client may request.
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# Only relevant if 'page_size_query_param' has also been set.
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max_page_size = None
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last_page_strings = ('last',)
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template = 'rest_framework/pagination/numbers.html'
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invalid_page_message = _('Invalid page.')
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def paginate_queryset(self, queryset, request, view=None):
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"""
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Paginate a queryset if required, either returning a
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page object, or `None` if pagination is not configured for this view.
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"""
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page_size = self.get_page_size(request)
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if not page_size:
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return None
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paginator = self.django_paginator_class(queryset, page_size)
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page_number = request.query_params.get(self.page_query_param, 1)
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if page_number in self.last_page_strings:
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page_number = paginator.num_pages
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try:
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self.page = paginator.page(page_number)
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except InvalidPage as exc:
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msg = self.invalid_page_message.format(
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page_number=page_number, message=six.text_type(exc)
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)
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raise NotFound(msg)
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if paginator.num_pages > 1 and self.template is not None:
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# The browsable API should display pagination controls.
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self.display_page_controls = True
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self.request = request
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return list(self.page)
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def get_paginated_response(self, data):
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return Response(OrderedDict([
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('count', self.page.paginator.count),
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('next', self.get_next_link()),
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('previous', self.get_previous_link()),
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('results', data)
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]))
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def get_page_size(self, request):
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if self.page_size_query_param:
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try:
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return _positive_int(
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request.query_params[self.page_size_query_param],
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strict=True,
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cutoff=self.max_page_size
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)
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except (KeyError, ValueError):
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pass
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return self.page_size
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def get_next_link(self):
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if not self.page.has_next():
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return None
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url = self.request.build_absolute_uri()
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page_number = self.page.next_page_number()
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return replace_query_param(url, self.page_query_param, page_number)
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def get_previous_link(self):
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if not self.page.has_previous():
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return None
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url = self.request.build_absolute_uri()
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page_number = self.page.previous_page_number()
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if page_number == 1:
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return remove_query_param(url, self.page_query_param)
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return replace_query_param(url, self.page_query_param, page_number)
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def get_html_context(self):
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base_url = self.request.build_absolute_uri()
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def page_number_to_url(page_number):
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if page_number == 1:
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return remove_query_param(base_url, self.page_query_param)
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else:
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return replace_query_param(base_url, self.page_query_param, page_number)
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current = self.page.number
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final = self.page.paginator.num_pages
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page_numbers = _get_displayed_page_numbers(current, final)
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page_links = _get_page_links(page_numbers, current, page_number_to_url)
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return {
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'previous_url': self.get_previous_link(),
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'next_url': self.get_next_link(),
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'page_links': page_links
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}
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def to_html(self):
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template = loader.get_template(self.template)
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context = self.get_html_context()
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return template_render(template, context)
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def get_fields(self, view):
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if self.page_size_query_param is None:
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return [self.page_query_param]
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return [self.page_query_param, self.page_size_query_param]
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class LimitOffsetPagination(BasePagination):
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"""
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A limit/offset based style. For example:
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http://api.example.org/accounts/?limit=100
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http://api.example.org/accounts/?offset=400&limit=100
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"""
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default_limit = api_settings.PAGE_SIZE
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limit_query_param = 'limit'
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offset_query_param = 'offset'
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max_limit = None
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template = 'rest_framework/pagination/numbers.html'
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def paginate_queryset(self, queryset, request, view=None):
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self.limit = self.get_limit(request)
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if self.limit is None:
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return None
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self.offset = self.get_offset(request)
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self.count = _get_count(queryset)
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self.request = request
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if self.count > self.limit and self.template is not None:
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self.display_page_controls = True
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if self.count == 0 or self.offset > self.count:
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return []
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return list(queryset[self.offset:self.offset + self.limit])
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def get_paginated_response(self, data):
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return Response(OrderedDict([
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('count', self.count),
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('next', self.get_next_link()),
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('previous', self.get_previous_link()),
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('results', data)
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]))
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def get_limit(self, request):
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if self.limit_query_param:
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try:
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return _positive_int(
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request.query_params[self.limit_query_param],
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strict=True,
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cutoff=self.max_limit
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)
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except (KeyError, ValueError):
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pass
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return self.default_limit
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def get_offset(self, request):
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try:
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return _positive_int(
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request.query_params[self.offset_query_param],
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)
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except (KeyError, ValueError):
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return 0
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def get_next_link(self):
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if self.offset + self.limit >= self.count:
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return None
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url = self.request.build_absolute_uri()
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url = replace_query_param(url, self.limit_query_param, self.limit)
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offset = self.offset + self.limit
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return replace_query_param(url, self.offset_query_param, offset)
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def get_previous_link(self):
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if self.offset <= 0:
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return None
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url = self.request.build_absolute_uri()
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url = replace_query_param(url, self.limit_query_param, self.limit)
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if self.offset - self.limit <= 0:
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return remove_query_param(url, self.offset_query_param)
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offset = self.offset - self.limit
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return replace_query_param(url, self.offset_query_param, offset)
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def get_html_context(self):
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base_url = self.request.build_absolute_uri()
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if self.limit:
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current = _divide_with_ceil(self.offset, self.limit) + 1
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# The number of pages is a little bit fiddly.
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# We need to sum both the number of pages from current offset to end
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# plus the number of pages up to the current offset.
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# When offset is not strictly divisible by the limit then we may
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# end up introducing an extra page as an artifact.
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final = (
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_divide_with_ceil(self.count - self.offset, self.limit) +
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_divide_with_ceil(self.offset, self.limit)
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)
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if final < 1:
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final = 1
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else:
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current = 1
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final = 1
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if current > final:
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current = final
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def page_number_to_url(page_number):
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if page_number == 1:
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return remove_query_param(base_url, self.offset_query_param)
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else:
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offset = self.offset + ((page_number - current) * self.limit)
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return replace_query_param(base_url, self.offset_query_param, offset)
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page_numbers = _get_displayed_page_numbers(current, final)
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page_links = _get_page_links(page_numbers, current, page_number_to_url)
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return {
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'previous_url': self.get_previous_link(),
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'next_url': self.get_next_link(),
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'page_links': page_links
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}
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def to_html(self):
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template = loader.get_template(self.template)
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context = self.get_html_context()
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return template_render(template, context)
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def get_fields(self, view):
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return [self.limit_query_param, self.offset_query_param]
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class CursorPagination(BasePagination):
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"""
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The cursor pagination implementation is necessarily complex.
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For an overview of the position/offset style we use, see this post:
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http://cramer.io/2011/03/08/building-cursors-for-the-disqus-api
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"""
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cursor_query_param = 'cursor'
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page_size = api_settings.PAGE_SIZE
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invalid_cursor_message = _('Invalid cursor')
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ordering = '-created'
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template = 'rest_framework/pagination/previous_and_next.html'
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# The offset in the cursor is used in situations where we have a
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# nearly-unique index. (Eg millisecond precision creation timestamps)
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# We guard against malicious users attempting to cause expensive database
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# queries, by having a hard cap on the maximum possible size of the offset.
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offset_cutoff = 1000
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def paginate_queryset(self, queryset, request, view=None):
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self.page_size = self.get_page_size(request)
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if not self.page_size:
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return None
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self.base_url = request.build_absolute_uri()
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self.ordering = self.get_ordering(request, queryset, view)
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self.cursor = self.decode_cursor(request)
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if self.cursor is None:
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(offset, reverse, current_position) = (0, False, None)
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else:
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(offset, reverse, current_position) = self.cursor
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# Cursor pagination always enforces an ordering.
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if reverse:
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queryset = queryset.order_by(*_reverse_ordering(self.ordering))
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else:
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queryset = queryset.order_by(*self.ordering)
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# If we have a cursor with a fixed position then filter by that.
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if current_position is not None:
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order = self.ordering[0]
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is_reversed = order.startswith('-')
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order_attr = order.lstrip('-')
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# Test for: (cursor reversed) XOR (queryset reversed)
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if self.cursor.reverse != is_reversed:
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kwargs = {order_attr + '__lt': current_position}
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else:
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kwargs = {order_attr + '__gt': current_position}
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queryset = queryset.filter(**kwargs)
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# If we have an offset cursor then offset the entire page by that amount.
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# We also always fetch an extra item in order to determine if there is a
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# page following on from this one.
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results = list(queryset[offset:offset + self.page_size + 1])
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self.page = list(results[:self.page_size])
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# Determine the position of the final item following the page.
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if len(results) > len(self.page):
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has_following_position = True
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following_position = self._get_position_from_instance(results[-1], self.ordering)
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else:
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has_following_position = False
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following_position = None
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# If we have a reverse queryset, then the query ordering was in reverse
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# so we need to reverse the items again before returning them to the user.
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if reverse:
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self.page = list(reversed(self.page))
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if reverse:
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# Determine next and previous positions for reverse cursors.
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self.has_next = (current_position is not None) or (offset > 0)
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self.has_previous = has_following_position
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if self.has_next:
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self.next_position = current_position
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if self.has_previous:
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self.previous_position = following_position
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else:
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# Determine next and previous positions for forward cursors.
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self.has_next = has_following_position
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self.has_previous = (current_position is not None) or (offset > 0)
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if self.has_next:
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self.next_position = following_position
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if self.has_previous:
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self.previous_position = current_position
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# Display page controls in the browsable API if there is more
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# than one page.
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if (self.has_previous or self.has_next) and self.template is not None:
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self.display_page_controls = True
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return self.page
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def get_page_size(self, request):
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return self.page_size
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def get_next_link(self):
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if not self.has_next:
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return None
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if self.cursor and self.cursor.reverse and self.cursor.offset != 0:
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# If we're reversing direction and we have an offset cursor
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|
# then we cannot use the first position we find as a marker.
|
|
compare = self._get_position_from_instance(self.page[-1], self.ordering)
|
|
else:
|
|
compare = self.next_position
|
|
offset = 0
|
|
|
|
for item in reversed(self.page):
|
|
position = self._get_position_from_instance(item, self.ordering)
|
|
if position != compare:
|
|
# The item in this position and the item following it
|
|
# have different positions. We can use this position as
|
|
# our marker.
|
|
break
|
|
|
|
# The item in this position has the same position as the item
|
|
# following it, we can't use it as a marker position, so increment
|
|
# the offset and keep seeking to the previous item.
|
|
compare = position
|
|
offset += 1
|
|
|
|
else:
|
|
# There were no unique positions in the page.
|
|
if not self.has_previous:
|
|
# We are on the first page.
|
|
# Our cursor will have an offset equal to the page size,
|
|
# but no position to filter against yet.
|
|
offset = self.page_size
|
|
position = None
|
|
elif self.cursor.reverse:
|
|
# The change in direction will introduce a paging artifact,
|
|
# where we end up skipping forward a few extra items.
|
|
offset = 0
|
|
position = self.previous_position
|
|
else:
|
|
# Use the position from the existing cursor and increment
|
|
# it's offset by the page size.
|
|
offset = self.cursor.offset + self.page_size
|
|
position = self.previous_position
|
|
|
|
cursor = Cursor(offset=offset, reverse=False, position=position)
|
|
return self.encode_cursor(cursor)
|
|
|
|
def get_previous_link(self):
|
|
if not self.has_previous:
|
|
return None
|
|
|
|
if self.cursor and not self.cursor.reverse and self.cursor.offset != 0:
|
|
# If we're reversing direction and we have an offset cursor
|
|
# then we cannot use the first position we find as a marker.
|
|
compare = self._get_position_from_instance(self.page[0], self.ordering)
|
|
else:
|
|
compare = self.previous_position
|
|
offset = 0
|
|
|
|
for item in self.page:
|
|
position = self._get_position_from_instance(item, self.ordering)
|
|
if position != compare:
|
|
# The item in this position and the item following it
|
|
# have different positions. We can use this position as
|
|
# our marker.
|
|
break
|
|
|
|
# The item in this position has the same position as the item
|
|
# following it, we can't use it as a marker position, so increment
|
|
# the offset and keep seeking to the previous item.
|
|
compare = position
|
|
offset += 1
|
|
|
|
else:
|
|
# There were no unique positions in the page.
|
|
if not self.has_next:
|
|
# We are on the final page.
|
|
# Our cursor will have an offset equal to the page size,
|
|
# but no position to filter against yet.
|
|
offset = self.page_size
|
|
position = None
|
|
elif self.cursor.reverse:
|
|
# Use the position from the existing cursor and increment
|
|
# it's offset by the page size.
|
|
offset = self.cursor.offset + self.page_size
|
|
position = self.next_position
|
|
else:
|
|
# The change in direction will introduce a paging artifact,
|
|
# where we end up skipping back a few extra items.
|
|
offset = 0
|
|
position = self.next_position
|
|
|
|
cursor = Cursor(offset=offset, reverse=True, position=position)
|
|
return self.encode_cursor(cursor)
|
|
|
|
def get_ordering(self, request, queryset, view):
|
|
"""
|
|
Return a tuple of strings, that may be used in an `order_by` method.
|
|
"""
|
|
ordering_filters = [
|
|
filter_cls for filter_cls in getattr(view, 'filter_backends', [])
|
|
if hasattr(filter_cls, 'get_ordering')
|
|
]
|
|
|
|
if ordering_filters:
|
|
# If a filter exists on the view that implements `get_ordering`
|
|
# then we defer to that filter to determine the ordering.
|
|
filter_cls = ordering_filters[0]
|
|
filter_instance = filter_cls()
|
|
ordering = filter_instance.get_ordering(request, queryset, view)
|
|
assert ordering is not None, (
|
|
'Using cursor pagination, but filter class {filter_cls} '
|
|
'returned a `None` ordering.'.format(
|
|
filter_cls=filter_cls.__name__
|
|
)
|
|
)
|
|
else:
|
|
# The default case is to check for an `ordering` attribute
|
|
# on this pagination instance.
|
|
ordering = self.ordering
|
|
assert ordering is not None, (
|
|
'Using cursor pagination, but no ordering attribute was declared '
|
|
'on the pagination class.'
|
|
)
|
|
assert '__' not in ordering, (
|
|
'Cursor pagination does not support double underscore lookups '
|
|
'for orderings. Orderings should be an unchanging, unique or '
|
|
'nearly-unique field on the model, such as "-created" or "pk".'
|
|
)
|
|
|
|
assert isinstance(ordering, (six.string_types, list, tuple)), (
|
|
'Invalid ordering. Expected string or tuple, but got {type}'.format(
|
|
type=type(ordering).__name__
|
|
)
|
|
)
|
|
|
|
if isinstance(ordering, six.string_types):
|
|
return (ordering,)
|
|
return tuple(ordering)
|
|
|
|
def decode_cursor(self, request):
|
|
"""
|
|
Given a request with a cursor, return a `Cursor` instance.
|
|
"""
|
|
# Determine if we have a cursor, and if so then decode it.
|
|
encoded = request.query_params.get(self.cursor_query_param)
|
|
if encoded is None:
|
|
return None
|
|
|
|
try:
|
|
querystring = b64decode(encoded.encode('ascii')).decode('ascii')
|
|
tokens = urlparse.parse_qs(querystring, keep_blank_values=True)
|
|
|
|
offset = tokens.get('o', ['0'])[0]
|
|
offset = _positive_int(offset, cutoff=self.offset_cutoff)
|
|
|
|
reverse = tokens.get('r', ['0'])[0]
|
|
reverse = bool(int(reverse))
|
|
|
|
position = tokens.get('p', [None])[0]
|
|
except (TypeError, ValueError):
|
|
raise NotFound(self.invalid_cursor_message)
|
|
|
|
return Cursor(offset=offset, reverse=reverse, position=position)
|
|
|
|
def encode_cursor(self, cursor):
|
|
"""
|
|
Given a Cursor instance, return an url with encoded cursor.
|
|
"""
|
|
tokens = {}
|
|
if cursor.offset != 0:
|
|
tokens['o'] = str(cursor.offset)
|
|
if cursor.reverse:
|
|
tokens['r'] = '1'
|
|
if cursor.position is not None:
|
|
tokens['p'] = cursor.position
|
|
|
|
querystring = urlparse.urlencode(tokens, doseq=True)
|
|
encoded = b64encode(querystring.encode('ascii')).decode('ascii')
|
|
return replace_query_param(self.base_url, self.cursor_query_param, encoded)
|
|
|
|
def _get_position_from_instance(self, instance, ordering):
|
|
attr = getattr(instance, ordering[0].lstrip('-'))
|
|
return six.text_type(attr)
|
|
|
|
def get_paginated_response(self, data):
|
|
return Response(OrderedDict([
|
|
('next', self.get_next_link()),
|
|
('previous', self.get_previous_link()),
|
|
('results', data)
|
|
]))
|
|
|
|
def get_html_context(self):
|
|
return {
|
|
'previous_url': self.get_previous_link(),
|
|
'next_url': self.get_next_link()
|
|
}
|
|
|
|
def to_html(self):
|
|
template = loader.get_template(self.template)
|
|
context = self.get_html_context()
|
|
return template_render(template, context)
|
|
|
|
def get_fields(self, view):
|
|
return [self.cursor_query_param]
|