diff options
Diffstat (limited to 'rest_framework/pagination.py')
| -rw-r--r-- | rest_framework/pagination.py | 67 |
1 files changed, 48 insertions, 19 deletions
diff --git a/rest_framework/pagination.py b/rest_framework/pagination.py index 3984da13..f56f55ce 100644 --- a/rest_framework/pagination.py +++ b/rest_framework/pagination.py @@ -1,3 +1,4 @@ +# coding: utf-8 """ Pagination serializers determine the structure of the output that should be used for paginated responses. @@ -385,7 +386,7 @@ Cursor = namedtuple('Cursor', ['offset', 'reverse', 'position']) def decode_cursor(encoded): - tokens = urlparse.parse_qs(b64decode(encoded)) + tokens = urlparse.parse_qs(b64decode(encoded), keep_blank_values=True) try: offset = int(tokens['offset'][0]) reverse = bool(int(tokens['reverse'][0])) @@ -406,8 +407,7 @@ def encode_cursor(cursor): class CursorPagination(BasePagination): - # reverse - # limit + # TODO: reverse cursors cursor_query_param = 'cursor' page_size = 5 @@ -417,26 +417,63 @@ class CursorPagination(BasePagination): encoded = request.query_params.get(self.cursor_query_param) if encoded is None: - cursor = None + self.cursor = None else: - cursor = decode_cursor(encoded) + self.cursor = decode_cursor(encoded) # TODO: Invalid cursors should 404 - if cursor is not None: - kwargs = {self.ordering + '__gt': cursor.position} + if self.cursor is not None and self.cursor.position != '': + kwargs = {self.ordering + '__gt': self.cursor.position} queryset = queryset.filter(**kwargs) - results = list(queryset[:self.page_size + 1]) + # The offset is used in order to deal with cases where we have + # items with an identical position. This allows the cursors + # to gracefully deal with non-unique fields as the ordering. + offset = 0 if (self.cursor is None) else self.cursor.offset + + # We fetch an extra item in order to determine if there is a next page. + results = list(queryset[offset:offset + self.page_size + 1]) self.page = results[:self.page_size] self.has_next = len(results) > len(self.page) + self.next_item = results[-1] if self.has_next else None return self.page def get_next_link(self): if not self.has_next: return None - last_item = self.page[-1] - position = self.get_position_from_instance(last_item, self.ordering) - cursor = Cursor(offset=0, reverse=False, position=position) + + compare = self.get_position_from_instance(self.next_item, self.ordering) + 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 postion 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: + if self.cursor is None: + # There were no unique positions in the page, and we were + # on the first page, ie. there was no existing cursor. + # Our cursor will have an offset equal to the page size, + # but no position to filter against yet. + offset = self.page_size + position = '' + else: + # There were no unique positions in the page. + # 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.cursor.position + + cursor = Cursor(offset=offset, reverse=False, position=position) encoded = encode_cursor(cursor) return replace_query_param(self.base_url, self.cursor_query_param, encoded) @@ -445,11 +482,3 @@ class CursorPagination(BasePagination): def get_position_from_instance(self, instance, ordering): return str(getattr(instance, ordering)) - - # def decode_cursor(self, encoded, ordering): - # items = urlparse.parse_qs(b64decode(encoded)) - # return items.get(ordering)[0] - - # def encode_cursor(self, cursor, ordering): - # items = [(ordering, cursor)] - # return b64encode(urlparse.urlencode(items, doseq=True)) |