Cursor pagination ordering

rest_framework/pagination.py

@@ -615,7 +615,7 @@ def paginate_queryset(self, queryset, request, view=None):
             return None
 
         self.base_url = request.build_absolute_uri()
-        self.ordering = self.get_ordering(request, queryset, view)
+        self.ordering = self.get_ordering()
 
         self.cursor = self.decode_cursor(request)
         if self.cursor is None:
@@ -624,10 +624,11 @@ def paginate_queryset(self, queryset, request, view=None):
             (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 not queryset.ordered:
+            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 current_position is not None:
@@ -801,41 +802,25 @@ def get_previous_link(self):
         cursor = Cursor(offset=offset, reverse=True, position=position)
         return self.encode_cursor(cursor)
 
-    def get_ordering(self, request, queryset, view):
+    def get_ordering(self):
         """
         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, (
+        assert self.ordering is not None, (
             'Using cursor pagination, but no ordering attribute was declared '
             'on the pagination class.'
         )
-        assert '__' not in ordering, (
+        assert '__' not in self.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)), (
+        assert isinstance(self.ordering, (str, list, tuple)), (
             'Invalid ordering. Expected string or tuple, but got {type}'.format(
-                type=type(ordering).__name__
+                type=type(self.ordering).__name__
             )
         )