mirror of
https://github.com/encode/django-rest-framework.git
synced 2024-11-24 18:44:00 +03:00
f1a11d41cb
* this commit fixes the usage of a CursorPagination combined with a view implementing an ordering filter, without a default ordering value. * former behavior was to fetch the ordering value from the filter, and raises an error if the value was None, preventing the fallback on the ordering set on the CursorPagination class itself. * we reversed the logic by getting first the value set on the class, and override it by the ordering filter if the parameter is present
984 lines
35 KiB
Python
984 lines
35 KiB
Python
"""
|
|
Pagination serializers determine the structure of the output that should
|
|
be used for paginated responses.
|
|
"""
|
|
|
|
import contextlib
|
|
from base64 import b64decode, b64encode
|
|
from collections import namedtuple
|
|
from urllib import parse
|
|
|
|
from django.core.paginator import InvalidPage
|
|
from django.core.paginator import Paginator as DjangoPaginator
|
|
from django.db.models import Q
|
|
from django.template import loader
|
|
from django.utils.encoding import force_str
|
|
from django.utils.translation import gettext_lazy as _
|
|
|
|
from rest_framework.compat import coreapi, coreschema
|
|
from rest_framework.exceptions import NotFound
|
|
from rest_framework.response import Response
|
|
from rest_framework.settings import api_settings
|
|
from rest_framework.utils.urls import remove_query_param, replace_query_param
|
|
|
|
|
|
def _positive_int(integer_string, strict=False, cutoff=None):
|
|
"""
|
|
Cast a string to a strictly positive integer.
|
|
"""
|
|
ret = int(integer_string)
|
|
if ret < 0 or (ret == 0 and strict):
|
|
raise ValueError()
|
|
if cutoff:
|
|
return min(ret, cutoff)
|
|
return ret
|
|
|
|
|
|
def _divide_with_ceil(a, b):
|
|
"""
|
|
Returns 'a' divided by 'b', with any remainder rounded up.
|
|
"""
|
|
if a % b:
|
|
return (a // b) + 1
|
|
|
|
return a // b
|
|
|
|
|
|
def _get_displayed_page_numbers(current, final):
|
|
"""
|
|
This utility function determines a list of page numbers to display.
|
|
This gives us a nice contextually relevant set of page numbers.
|
|
|
|
For example:
|
|
current=14, final=16 -> [1, None, 13, 14, 15, 16]
|
|
|
|
This implementation gives one page to each side of the cursor,
|
|
or two pages to the side when the cursor is at the edge, then
|
|
ensures that any breaks between non-continuous page numbers never
|
|
remove only a single page.
|
|
|
|
For an alternative implementation which gives two pages to each side of
|
|
the cursor, eg. as in GitHub issue list pagination, see:
|
|
|
|
https://gist.github.com/tomchristie/321140cebb1c4a558b15
|
|
"""
|
|
assert current >= 1
|
|
assert final >= current
|
|
|
|
if final <= 5:
|
|
return list(range(1, final + 1))
|
|
|
|
# We always include the first two pages, last two pages, and
|
|
# two pages either side of the current page.
|
|
included = {1, current - 1, current, current + 1, final}
|
|
|
|
# If the break would only exclude a single page number then we
|
|
# may as well include the page number instead of the break.
|
|
if current <= 4:
|
|
included.add(2)
|
|
included.add(3)
|
|
if current >= final - 3:
|
|
included.add(final - 1)
|
|
included.add(final - 2)
|
|
|
|
# Now sort the page numbers and drop anything outside the limits.
|
|
included = [
|
|
idx for idx in sorted(included)
|
|
if 0 < idx <= final
|
|
]
|
|
|
|
# Finally insert any `...` breaks
|
|
if current > 4:
|
|
included.insert(1, None)
|
|
if current < final - 3:
|
|
included.insert(len(included) - 1, None)
|
|
return included
|
|
|
|
|
|
def _get_page_links(page_numbers, current, url_func):
|
|
"""
|
|
Given a list of page numbers and `None` page breaks,
|
|
return a list of `PageLink` objects.
|
|
"""
|
|
page_links = []
|
|
for page_number in page_numbers:
|
|
if page_number is None:
|
|
page_link = PAGE_BREAK
|
|
else:
|
|
page_link = PageLink(
|
|
url=url_func(page_number),
|
|
number=page_number,
|
|
is_active=(page_number == current),
|
|
is_break=False
|
|
)
|
|
page_links.append(page_link)
|
|
return page_links
|
|
|
|
|
|
def _reverse_ordering(ordering_tuple):
|
|
"""
|
|
Given an order_by tuple such as `('-created', 'uuid')` reverse the
|
|
ordering and return a new tuple, eg. `('created', '-uuid')`.
|
|
"""
|
|
def invert(x):
|
|
return x[1:] if x.startswith('-') else '-' + x
|
|
|
|
return tuple([invert(item) for item in ordering_tuple])
|
|
|
|
|
|
Cursor = namedtuple('Cursor', ['offset', 'reverse', 'position'])
|
|
PageLink = namedtuple('PageLink', ['url', 'number', 'is_active', 'is_break'])
|
|
|
|
PAGE_BREAK = PageLink(url=None, number=None, is_active=False, is_break=True)
|
|
|
|
|
|
class BasePagination:
|
|
display_page_controls = False
|
|
|
|
def paginate_queryset(self, queryset, request, view=None): # pragma: no cover
|
|
raise NotImplementedError('paginate_queryset() must be implemented.')
|
|
|
|
def get_paginated_response(self, data): # pragma: no cover
|
|
raise NotImplementedError('get_paginated_response() must be implemented.')
|
|
|
|
def get_paginated_response_schema(self, schema):
|
|
return schema
|
|
|
|
def to_html(self): # pragma: no cover
|
|
raise NotImplementedError('to_html() must be implemented to display page controls.')
|
|
|
|
def get_results(self, data):
|
|
return data['results']
|
|
|
|
def get_schema_fields(self, view):
|
|
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'
|
|
return []
|
|
|
|
def get_schema_operation_parameters(self, view):
|
|
return []
|
|
|
|
|
|
class PageNumberPagination(BasePagination):
|
|
"""
|
|
A simple page number based style that supports page numbers as
|
|
query parameters. For example:
|
|
|
|
http://api.example.org/accounts/?page=4
|
|
http://api.example.org/accounts/?page=4&page_size=100
|
|
"""
|
|
# The default page size.
|
|
# Defaults to `None`, meaning pagination is disabled.
|
|
page_size = api_settings.PAGE_SIZE
|
|
|
|
django_paginator_class = DjangoPaginator
|
|
|
|
# Client can control the page using this query parameter.
|
|
page_query_param = 'page'
|
|
page_query_description = _('A page number within the paginated result set.')
|
|
|
|
# Client can control the page size using this query parameter.
|
|
# Default is 'None'. Set to eg 'page_size' to enable usage.
|
|
page_size_query_param = None
|
|
page_size_query_description = _('Number of results to return per page.')
|
|
|
|
# Set to an integer to limit the maximum page size the client may request.
|
|
# Only relevant if 'page_size_query_param' has also been set.
|
|
max_page_size = None
|
|
|
|
last_page_strings = ('last',)
|
|
|
|
template = 'rest_framework/pagination/numbers.html'
|
|
|
|
invalid_page_message = _('Invalid page.')
|
|
|
|
def paginate_queryset(self, queryset, request, view=None):
|
|
"""
|
|
Paginate a queryset if required, either returning a
|
|
page object, or `None` if pagination is not configured for this view.
|
|
"""
|
|
self.request = request
|
|
page_size = self.get_page_size(request)
|
|
if not page_size:
|
|
return None
|
|
|
|
paginator = self.django_paginator_class(queryset, page_size)
|
|
page_number = self.get_page_number(request, paginator)
|
|
|
|
try:
|
|
self.page = paginator.page(page_number)
|
|
except InvalidPage as exc:
|
|
msg = self.invalid_page_message.format(
|
|
page_number=page_number, message=str(exc)
|
|
)
|
|
raise NotFound(msg)
|
|
|
|
if paginator.num_pages > 1 and self.template is not None:
|
|
# The browsable API should display pagination controls.
|
|
self.display_page_controls = True
|
|
|
|
return list(self.page)
|
|
|
|
def get_page_number(self, request, paginator):
|
|
page_number = request.query_params.get(self.page_query_param) or 1
|
|
if page_number in self.last_page_strings:
|
|
page_number = paginator.num_pages
|
|
return page_number
|
|
|
|
def get_paginated_response(self, data):
|
|
return Response({
|
|
'count': self.page.paginator.count,
|
|
'next': self.get_next_link(),
|
|
'previous': self.get_previous_link(),
|
|
'results': data,
|
|
})
|
|
|
|
def get_paginated_response_schema(self, schema):
|
|
return {
|
|
'type': 'object',
|
|
'properties': {
|
|
'count': {
|
|
'type': 'integer',
|
|
'example': 123,
|
|
},
|
|
'next': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{page_query_param}=4'.format(
|
|
page_query_param=self.page_query_param)
|
|
},
|
|
'previous': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{page_query_param}=2'.format(
|
|
page_query_param=self.page_query_param)
|
|
},
|
|
'results': schema,
|
|
},
|
|
}
|
|
|
|
def get_page_size(self, request):
|
|
if self.page_size_query_param:
|
|
with contextlib.suppress(KeyError, ValueError):
|
|
return _positive_int(
|
|
request.query_params[self.page_size_query_param],
|
|
strict=True,
|
|
cutoff=self.max_page_size
|
|
)
|
|
return self.page_size
|
|
|
|
def get_next_link(self):
|
|
if not self.page.has_next():
|
|
return None
|
|
url = self.request.build_absolute_uri()
|
|
page_number = self.page.next_page_number()
|
|
return replace_query_param(url, self.page_query_param, page_number)
|
|
|
|
def get_previous_link(self):
|
|
if not self.page.has_previous():
|
|
return None
|
|
url = self.request.build_absolute_uri()
|
|
page_number = self.page.previous_page_number()
|
|
if page_number == 1:
|
|
return remove_query_param(url, self.page_query_param)
|
|
return replace_query_param(url, self.page_query_param, page_number)
|
|
|
|
def get_html_context(self):
|
|
base_url = self.request.build_absolute_uri()
|
|
|
|
def page_number_to_url(page_number):
|
|
if page_number == 1:
|
|
return remove_query_param(base_url, self.page_query_param)
|
|
else:
|
|
return replace_query_param(base_url, self.page_query_param, page_number)
|
|
|
|
current = self.page.number
|
|
final = self.page.paginator.num_pages
|
|
page_numbers = _get_displayed_page_numbers(current, final)
|
|
page_links = _get_page_links(page_numbers, current, page_number_to_url)
|
|
|
|
return {
|
|
'previous_url': self.get_previous_link(),
|
|
'next_url': self.get_next_link(),
|
|
'page_links': page_links
|
|
}
|
|
|
|
def to_html(self):
|
|
template = loader.get_template(self.template)
|
|
context = self.get_html_context()
|
|
return template.render(context)
|
|
|
|
def get_schema_fields(self, view):
|
|
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'
|
|
assert coreschema is not None, 'coreschema must be installed to use `get_schema_fields()`'
|
|
fields = [
|
|
coreapi.Field(
|
|
name=self.page_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.Integer(
|
|
title='Page',
|
|
description=force_str(self.page_query_description)
|
|
)
|
|
)
|
|
]
|
|
if self.page_size_query_param is not None:
|
|
fields.append(
|
|
coreapi.Field(
|
|
name=self.page_size_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.Integer(
|
|
title='Page size',
|
|
description=force_str(self.page_size_query_description)
|
|
)
|
|
)
|
|
)
|
|
return fields
|
|
|
|
def get_schema_operation_parameters(self, view):
|
|
parameters = [
|
|
{
|
|
'name': self.page_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.page_query_description),
|
|
'schema': {
|
|
'type': 'integer',
|
|
},
|
|
},
|
|
]
|
|
if self.page_size_query_param is not None:
|
|
parameters.append(
|
|
{
|
|
'name': self.page_size_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.page_size_query_description),
|
|
'schema': {
|
|
'type': 'integer',
|
|
},
|
|
},
|
|
)
|
|
return parameters
|
|
|
|
|
|
class LimitOffsetPagination(BasePagination):
|
|
"""
|
|
A limit/offset based style. For example:
|
|
|
|
http://api.example.org/accounts/?limit=100
|
|
http://api.example.org/accounts/?offset=400&limit=100
|
|
"""
|
|
default_limit = api_settings.PAGE_SIZE
|
|
limit_query_param = 'limit'
|
|
limit_query_description = _('Number of results to return per page.')
|
|
offset_query_param = 'offset'
|
|
offset_query_description = _('The initial index from which to return the results.')
|
|
max_limit = None
|
|
template = 'rest_framework/pagination/numbers.html'
|
|
|
|
def paginate_queryset(self, queryset, request, view=None):
|
|
self.request = request
|
|
self.limit = self.get_limit(request)
|
|
if self.limit is None:
|
|
return None
|
|
|
|
self.count = self.get_count(queryset)
|
|
self.offset = self.get_offset(request)
|
|
if self.count > self.limit and self.template is not None:
|
|
self.display_page_controls = True
|
|
|
|
if self.count == 0 or self.offset > self.count:
|
|
return []
|
|
return list(queryset[self.offset:self.offset + self.limit])
|
|
|
|
def get_paginated_response(self, data):
|
|
return Response({
|
|
'count': self.count,
|
|
'next': self.get_next_link(),
|
|
'previous': self.get_previous_link(),
|
|
'results': data
|
|
})
|
|
|
|
def get_paginated_response_schema(self, schema):
|
|
return {
|
|
'type': 'object',
|
|
'properties': {
|
|
'count': {
|
|
'type': 'integer',
|
|
'example': 123,
|
|
},
|
|
'next': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{offset_param}=400&{limit_param}=100'.format(
|
|
offset_param=self.offset_query_param, limit_param=self.limit_query_param),
|
|
},
|
|
'previous': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{offset_param}=200&{limit_param}=100'.format(
|
|
offset_param=self.offset_query_param, limit_param=self.limit_query_param),
|
|
},
|
|
'results': schema,
|
|
},
|
|
}
|
|
|
|
def get_limit(self, request):
|
|
if self.limit_query_param:
|
|
with contextlib.suppress(KeyError, ValueError):
|
|
return _positive_int(
|
|
request.query_params[self.limit_query_param],
|
|
strict=True,
|
|
cutoff=self.max_limit
|
|
)
|
|
return self.default_limit
|
|
|
|
def get_offset(self, request):
|
|
try:
|
|
return _positive_int(
|
|
request.query_params[self.offset_query_param],
|
|
)
|
|
except (KeyError, ValueError):
|
|
return 0
|
|
|
|
def get_next_link(self):
|
|
if self.offset + self.limit >= self.count:
|
|
return None
|
|
|
|
url = self.request.build_absolute_uri()
|
|
url = replace_query_param(url, self.limit_query_param, self.limit)
|
|
|
|
offset = self.offset + self.limit
|
|
return replace_query_param(url, self.offset_query_param, offset)
|
|
|
|
def get_previous_link(self):
|
|
if self.offset <= 0:
|
|
return None
|
|
|
|
url = self.request.build_absolute_uri()
|
|
url = replace_query_param(url, self.limit_query_param, self.limit)
|
|
|
|
if self.offset - self.limit <= 0:
|
|
return remove_query_param(url, self.offset_query_param)
|
|
|
|
offset = self.offset - self.limit
|
|
return replace_query_param(url, self.offset_query_param, offset)
|
|
|
|
def get_html_context(self):
|
|
base_url = self.request.build_absolute_uri()
|
|
|
|
if self.limit:
|
|
current = _divide_with_ceil(self.offset, self.limit) + 1
|
|
|
|
# The number of pages is a little bit fiddly.
|
|
# We need to sum both the number of pages from current offset to end
|
|
# plus the number of pages up to the current offset.
|
|
# When offset is not strictly divisible by the limit then we may
|
|
# end up introducing an extra page as an artifact.
|
|
final = (
|
|
_divide_with_ceil(self.count - self.offset, self.limit) +
|
|
_divide_with_ceil(self.offset, self.limit)
|
|
)
|
|
|
|
final = max(final, 1)
|
|
else:
|
|
current = 1
|
|
final = 1
|
|
|
|
if current > final:
|
|
current = final
|
|
|
|
def page_number_to_url(page_number):
|
|
if page_number == 1:
|
|
return remove_query_param(base_url, self.offset_query_param)
|
|
else:
|
|
offset = self.offset + ((page_number - current) * self.limit)
|
|
return replace_query_param(base_url, self.offset_query_param, offset)
|
|
|
|
page_numbers = _get_displayed_page_numbers(current, final)
|
|
page_links = _get_page_links(page_numbers, current, page_number_to_url)
|
|
|
|
return {
|
|
'previous_url': self.get_previous_link(),
|
|
'next_url': self.get_next_link(),
|
|
'page_links': page_links
|
|
}
|
|
|
|
def to_html(self):
|
|
template = loader.get_template(self.template)
|
|
context = self.get_html_context()
|
|
return template.render(context)
|
|
|
|
def get_count(self, queryset):
|
|
"""
|
|
Determine an object count, supporting either querysets or regular lists.
|
|
"""
|
|
try:
|
|
return queryset.count()
|
|
except (AttributeError, TypeError):
|
|
return len(queryset)
|
|
|
|
def get_schema_fields(self, view):
|
|
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'
|
|
assert coreschema is not None, 'coreschema must be installed to use `get_schema_fields()`'
|
|
return [
|
|
coreapi.Field(
|
|
name=self.limit_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.Integer(
|
|
title='Limit',
|
|
description=force_str(self.limit_query_description)
|
|
)
|
|
),
|
|
coreapi.Field(
|
|
name=self.offset_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.Integer(
|
|
title='Offset',
|
|
description=force_str(self.offset_query_description)
|
|
)
|
|
)
|
|
]
|
|
|
|
def get_schema_operation_parameters(self, view):
|
|
parameters = [
|
|
{
|
|
'name': self.limit_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.limit_query_description),
|
|
'schema': {
|
|
'type': 'integer',
|
|
},
|
|
},
|
|
{
|
|
'name': self.offset_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.offset_query_description),
|
|
'schema': {
|
|
'type': 'integer',
|
|
},
|
|
},
|
|
]
|
|
return parameters
|
|
|
|
|
|
class CursorPagination(BasePagination):
|
|
"""
|
|
The cursor pagination implementation is necessarily complex.
|
|
For an overview of the position/offset style we use, see this post:
|
|
https://cra.mr/2011/03/08/building-cursors-for-the-disqus-api
|
|
"""
|
|
cursor_query_param = 'cursor'
|
|
cursor_query_description = _('The pagination cursor value.')
|
|
page_size = api_settings.PAGE_SIZE
|
|
invalid_cursor_message = _('Invalid cursor')
|
|
ordering = '-created'
|
|
template = 'rest_framework/pagination/previous_and_next.html'
|
|
|
|
# Client can control the page size using this query parameter.
|
|
# Default is 'None'. Set to eg 'page_size' to enable usage.
|
|
page_size_query_param = None
|
|
page_size_query_description = _('Number of results to return per page.')
|
|
|
|
# Set to an integer to limit the maximum page size the client may request.
|
|
# Only relevant if 'page_size_query_param' has also been set.
|
|
max_page_size = None
|
|
|
|
# The offset in the cursor is used in situations where we have a
|
|
# nearly-unique index. (Eg millisecond precision creation timestamps)
|
|
# We guard against malicious users attempting to cause expensive database
|
|
# queries, by having a hard cap on the maximum possible size of the offset.
|
|
offset_cutoff = 1000
|
|
|
|
def paginate_queryset(self, queryset, request, view=None):
|
|
self.request = request
|
|
self.page_size = self.get_page_size(request)
|
|
if not self.page_size:
|
|
return None
|
|
|
|
self.base_url = request.build_absolute_uri()
|
|
self.ordering = self.get_ordering(request, queryset, view)
|
|
|
|
self.cursor = self.decode_cursor(request)
|
|
if self.cursor is None:
|
|
(offset, reverse, current_position) = (0, False, None)
|
|
else:
|
|
(offset, reverse, current_position) = self.cursor
|
|
|
|
# Cursor pagination always enforces an ordering.
|
|
if reverse:
|
|
queryset = queryset.order_by(*_reverse_ordering(self.ordering))
|
|
else:
|
|
queryset = queryset.order_by(*self.ordering)
|
|
|
|
# If we have a cursor with a fixed position then filter by that.
|
|
if str(current_position) != 'None':
|
|
order = self.ordering[0]
|
|
is_reversed = order.startswith('-')
|
|
order_attr = order.lstrip('-')
|
|
|
|
# Test for: (cursor reversed) XOR (queryset reversed)
|
|
if self.cursor.reverse != is_reversed:
|
|
kwargs = {order_attr + '__lt': current_position}
|
|
else:
|
|
kwargs = {order_attr + '__gt': current_position}
|
|
|
|
filter_query = Q(**kwargs)
|
|
# If some records contain a null for the ordering field, don't lose them.
|
|
# When reverse ordering, nulls will come last and need to be included.
|
|
if (reverse and not is_reversed) or is_reversed:
|
|
filter_query |= Q(**{order_attr + '__isnull': True})
|
|
queryset = queryset.filter(filter_query)
|
|
|
|
# If we have an offset cursor then offset the entire page by that amount.
|
|
# We also always fetch an extra item in order to determine if there is a
|
|
# page following on from this one.
|
|
results = list(queryset[offset:offset + self.page_size + 1])
|
|
self.page = list(results[:self.page_size])
|
|
|
|
# Determine the position of the final item following the page.
|
|
if len(results) > len(self.page):
|
|
has_following_position = True
|
|
following_position = self._get_position_from_instance(results[-1], self.ordering)
|
|
else:
|
|
has_following_position = False
|
|
following_position = None
|
|
|
|
if reverse:
|
|
# If we have a reverse queryset, then the query ordering was in reverse
|
|
# so we need to reverse the items again before returning them to the user.
|
|
self.page = list(reversed(self.page))
|
|
|
|
# Determine next and previous positions for reverse cursors.
|
|
self.has_next = (current_position is not None) or (offset > 0)
|
|
self.has_previous = has_following_position
|
|
if self.has_next:
|
|
self.next_position = current_position
|
|
if self.has_previous:
|
|
self.previous_position = following_position
|
|
else:
|
|
# Determine next and previous positions for forward cursors.
|
|
self.has_next = has_following_position
|
|
self.has_previous = (current_position is not None) or (offset > 0)
|
|
if self.has_next:
|
|
self.next_position = following_position
|
|
if self.has_previous:
|
|
self.previous_position = current_position
|
|
|
|
# Display page controls in the browsable API if there is more
|
|
# than one page.
|
|
if (self.has_previous or self.has_next) and self.template is not None:
|
|
self.display_page_controls = True
|
|
|
|
return self.page
|
|
|
|
def get_page_size(self, request):
|
|
if self.page_size_query_param:
|
|
with contextlib.suppress(KeyError, ValueError):
|
|
return _positive_int(
|
|
request.query_params[self.page_size_query_param],
|
|
strict=True,
|
|
cutoff=self.max_page_size
|
|
)
|
|
return self.page_size
|
|
|
|
def get_next_link(self):
|
|
if not self.has_next:
|
|
return None
|
|
|
|
if self.page and self.cursor and 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[-1], self.ordering)
|
|
else:
|
|
compare = self.next_position
|
|
offset = 0
|
|
|
|
has_item_with_unique_position = False
|
|
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.
|
|
has_item_with_unique_position = position is not None
|
|
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
|
|
|
|
if self.page and not has_item_with_unique_position:
|
|
# 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
|
|
|
|
if not self.page:
|
|
position = self.next_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.page and 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
|
|
|
|
has_item_with_unique_position = False
|
|
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.
|
|
has_item_with_unique_position = position is not None
|
|
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
|
|
|
|
if self.page and not has_item_with_unique_position:
|
|
# 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
|
|
|
|
if not self.page:
|
|
position = self.previous_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.
|
|
"""
|
|
# The default case is to check for an `ordering` attribute
|
|
# on this pagination instance.
|
|
ordering = self.ordering
|
|
|
|
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_from_filter = filter_instance.get_ordering(request, queryset, view)
|
|
if ordering_from_filter:
|
|
ordering = ordering_from_filter
|
|
|
|
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, (str, list, tuple)), (
|
|
'Invalid ordering. Expected string or tuple, but got {type}'.format(
|
|
type=type(ordering).__name__
|
|
)
|
|
)
|
|
|
|
if isinstance(ordering, str):
|
|
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 = parse.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 = parse.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):
|
|
field_name = ordering[0].lstrip('-')
|
|
if isinstance(instance, dict):
|
|
attr = instance[field_name]
|
|
else:
|
|
attr = getattr(instance, field_name)
|
|
return None if attr is None else str(attr)
|
|
|
|
def get_paginated_response(self, data):
|
|
return Response({
|
|
'next': self.get_next_link(),
|
|
'previous': self.get_previous_link(),
|
|
'results': data,
|
|
})
|
|
|
|
def get_paginated_response_schema(self, schema):
|
|
return {
|
|
'type': 'object',
|
|
'properties': {
|
|
'next': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{cursor_query_param}=cD00ODY%3D"'.format(
|
|
cursor_query_param=self.cursor_query_param)
|
|
},
|
|
'previous': {
|
|
'type': 'string',
|
|
'nullable': True,
|
|
'format': 'uri',
|
|
'example': 'http://api.example.org/accounts/?{cursor_query_param}=cj0xJnA9NDg3'.format(
|
|
cursor_query_param=self.cursor_query_param)
|
|
},
|
|
'results': schema,
|
|
},
|
|
}
|
|
|
|
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(context)
|
|
|
|
def get_schema_fields(self, view):
|
|
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'
|
|
assert coreschema is not None, 'coreschema must be installed to use `get_schema_fields()`'
|
|
fields = [
|
|
coreapi.Field(
|
|
name=self.cursor_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.String(
|
|
title='Cursor',
|
|
description=force_str(self.cursor_query_description)
|
|
)
|
|
)
|
|
]
|
|
if self.page_size_query_param is not None:
|
|
fields.append(
|
|
coreapi.Field(
|
|
name=self.page_size_query_param,
|
|
required=False,
|
|
location='query',
|
|
schema=coreschema.Integer(
|
|
title='Page size',
|
|
description=force_str(self.page_size_query_description)
|
|
)
|
|
)
|
|
)
|
|
return fields
|
|
|
|
def get_schema_operation_parameters(self, view):
|
|
parameters = [
|
|
{
|
|
'name': self.cursor_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.cursor_query_description),
|
|
'schema': {
|
|
'type': 'string',
|
|
},
|
|
}
|
|
]
|
|
if self.page_size_query_param is not None:
|
|
parameters.append(
|
|
{
|
|
'name': self.page_size_query_param,
|
|
'required': False,
|
|
'in': 'query',
|
|
'description': force_str(self.page_size_query_description),
|
|
'schema': {
|
|
'type': 'integer',
|
|
},
|
|
}
|
|
)
|
|
return parameters
|