fixes

Author: timgraham

README.md

@@ -121,6 +121,8 @@ Migrations for 'admin':
 - `Subquery`, `Exists`, and using a `QuerySet` in `QuerySet.annotate()` aren't
   supported.
 
+* Ordering a `QuerySet` by `nulls_first` or `nulls_last` isn't supported.
+
 - `DateTimeField` doesn't support microsecond precision, and correspondingly,
   `DurationField` stores milliseconds rather than microseconds.
 

django_mongodb/compiler.py

@@ -4,7 +4,7 @@
 from django.db.models.aggregates import Aggregate
 from django.db.models.expressions import OrderBy
 from django.db.models.sql import compiler
-from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, MULTI
+from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, MULTI, ORDER_DIR
 from django.utils.functional import cached_property
 
 from .base import Cursor
@@ -199,32 +199,34 @@ def _get_ordering(self):
             if self.query.default_ordering
             else self.query.order_by
         )
-
         if not ordering:
             return self.query.standard_ordering
-
+        default_order, _ = ORDER_DIR["ASC" if self.query.standard_ordering else "DESC"]
         column_ordering = []
+        columns_seen = set()
         for order in ordering:
             if order == "?":
                 raise NotSupportedError("Randomized ordering isn't supported by MongoDB.")
             if hasattr(order, "resolve_expression"):
                 orderby = order if isinstance(order, OrderBy) else order.asc()
                 orderby = orderby.resolve_expression(self.query, allow_joins=True, reuse=None)
                 ascending = not orderby.descending
+                # If the query is reversed, ascending and descending are inverted.
+                if not self.query.standard_ordering:
+                    ascending = not ascending
             else:
-                ascending = not order.startswith("-")
-                name = order.lstrip("+-")
-                if name == "pk":
-                    name = opts.pk.name
-                orderby, _ = self.find_ordering_name(order, self.query.get_meta())[0]
+                orderby, _ = self.find_ordering_name(
+                    order, self.query.get_meta(), default_order=default_order
+                )[0]
+                ascending = not orderby.descending
             column = orderby.expression.as_mql(self, self.connection)
             if isinstance(column, dict):
                 raise NotSupportedError("order_by() expression not supported.")
             column = column.removeprefix("$")
-            # If the query is reversed, ascending and descending are inverted.
-            if not self.query.standard_ordering:
-                ascending = not ascending
-            column_ordering.append((column, ascending))
+            # Don't add the same column twice.
+            if column not in columns_seen:
+                columns_seen.add(column)
+                column_ordering.append((column, ascending))
         return column_ordering
 
     @cached_property

django_mongodb/expressions.py

@@ -12,6 +12,7 @@
     F,
     NegatedExpression,
     Ref,
+    ResolvedOuterRef,
     Subquery,
     Value,
     When,
@@ -111,6 +112,7 @@ def register_expressions():
     NegatedExpression.as_mql = negated_expression
     Query.as_mql = query
     Ref.as_mql = ref
+    ResolvedOuterRef.as_mql = ResolvedOuterRef.as_sql
     Subquery.as_mql = subquery
     When.as_mql = when
     Value.as_mql = value

django_mongodb/features.py

@@ -47,15 +47,10 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "ordering.tests.OrderingTests.test_order_by_expr_query_reuse",
         "ordering.tests.OrderingTests.test_order_by_expression_ref",
         "ordering.tests.OrderingTests.test_ordering_select_related_collision",
+        "queries.tests.Queries1Tests.test_order_by_related_field_transform",
         "update.tests.AdvancedTests.test_update_ordered_by_inline_m2m_annotation",
         "update.tests.AdvancedTests.test_update_ordered_by_m2m_annotation",
         "update.tests.AdvancedTests.test_update_ordered_by_m2m_annotation_desc",
-        # Wrong results for ordering queries.
-        "ordering.tests.OrderingTests.test_order_by_f_expression_duplicates",
-        "ordering.tests.OrderingTests.test_order_by_nulls_first",
-        "ordering.tests.OrderingTests.test_order_by_nulls_last",
-        "ordering.tests.OrderingTests.test_order_by_self_referential_fk",
-        "ordering.tests.OrderingTests.test_related_ordering_duplicate_table_reference",
         # pymongo: ValueError: update cannot be empty
         "update.tests.SimpleTest.test_empty_update_with_inheritance",
         "update.tests.SimpleTest.test_nonempty_update_with_inheritance",
@@ -127,15 +122,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # QuerySet.explain() not implemented:
         # https://github.com/mongodb-labs/django-mongodb/issues/28
         "queries.test_explain.ExplainUnsupportedTests.test_message",
-        # Ordering by related transform not supported.
-        "queries.tests.Queries1Tests.test_order_by_related_field_transform",
-        # Ordering on a related field should use the remote model's default
-        # ordering as a final step.
-        "queries.tests.Queries1Tests.test_tickets_2076_7256",
         # filter() on related model + update() doesn't work.
         "queries.tests.Queries5Tests.test_ticket9848",
-        # ???
-        "expressions.tests.BasicExpressionsTests.test_outerref",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {
@@ -472,7 +460,6 @@ def django_test_expected_failures(self):
         },
         "QuerySet.distinct() is not supported.": {
             "lookup.tests.LookupTests.test_lookup_collision_distinct",
-            "ordering.tests.OrderingTests.test_orders_nulls_first_on_filtered_subquery",
             "queries.tests.ExcludeTest17600.test_exclude_plain_distinct",
             "queries.tests.ExcludeTest17600.test_exclude_with_q_is_equal_to_plain_exclude",
             "queries.tests.ExcludeTest17600.test_exclude_with_q_object_distinct",
@@ -516,6 +503,11 @@ def django_test_expected_failures(self):
             "queries.tests.ValuesQuerysetTests.test_named_values_list_without_fields",
             "select_related.tests.SelectRelatedTests.test_select_related_with_extra",
         },
+        "Ordering a QuerySet by null_first/nulls_last is not supported on MongoDB.": {
+            "ordering.tests.OrderingTests.test_order_by_nulls_first",
+            "ordering.tests.OrderingTests.test_order_by_nulls_last",
+            "ordering.tests.OrderingTests.test_orders_nulls_first_on_filtered_subquery",
+        },
         "QuerySet.update() crash: Unrecognized expression '$count'": {
             "update.tests.AdvancedTests.test_update_annotated_multi_table_queryset",
         },

django_mongodb/operations.py

@@ -6,9 +6,9 @@
 
 from bson.decimal128 import Decimal128
 from django.conf import settings
-from django.db import DataError
+from django.db import DataError, NotSupportedError
 from django.db.backends.base.operations import BaseDatabaseOperations
-from django.db.models.expressions import Combinable
+from django.db.models.expressions import Combinable, OrderBy
 from django.utils import timezone
 from django.utils.regex_helper import _lazy_re_compile
 
@@ -140,6 +140,11 @@ def convert_uuidfield_value(self, value, expression, connection):
             value = uuid.UUID(value)
         return value
 
+    def check_expression_support(self, expression):
+        if isinstance(expression, OrderBy) and (expression.nulls_first or expression.nulls_last):
+            option = "null_first" if expression.nulls_first else "nulls_last"
+            raise NotSupportedError(f"Ordering a QuerySet by {option} is not supported on MongoDB.")
+
     def combine_expression(self, connector, sub_expressions):
         lhs, rhs = sub_expressions
         if connector == Combinable.BITLEFTSHIFT: