Enforce ordering only when queryset is not ordered

Author: ulgens

rest_framework/pagination.py

@@ -615,7 +615,6 @@ 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.cursor = self.decode_cursor(request)
         if self.cursor is None:
@@ -624,10 +623,13 @@ 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:
+            self.ordering = self.get_ordering(request, queryset, view)
+
+            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:

tests/test_pagination.py

@@ -969,8 +969,9 @@ def __init__(self, idx):
                 self.created = idx
 
         class MockQuerySet:
-            def __init__(self, items):
+            def __init__(self, items, ordered=False):
                 self.items = items
+                self.ordered = ordered
 
             def filter(self, created__gt=None, created__lt=None):
                 if created__gt is not None:
@@ -987,7 +988,7 @@ def filter(self, created__gt=None, created__lt=None):
 
             def order_by(self, *ordering):
                 if ordering[0].startswith('-'):
-                    return MockQuerySet(list(reversed(self.items)))
+                    return MockQuerySet(list(reversed(self.items)), ordered=True)
                 return self
 
             def __getitem__(self, sliced):