add support for order_by() on related collections

Author: timgraham

.github/workflows/test-python.yml

@@ -47,7 +47,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: 'mongodb-forks/django'
-          ref: 'mongodb-5.0.x'
+          ref: 'related-ordering'
           path: 'django_repo'
       - name: Install system packages for Django's Python test dependencies
         run: |

django_mongodb/compiler.py

@@ -205,8 +205,6 @@ def _get_ordering(self):
 
         column_ordering = []
         for order in ordering:
-            if LOOKUP_SEP in order:
-                raise NotSupportedError("Ordering can't span tables on MongoDB (%s)." % order)
             if order == "?":
                 raise NotSupportedError("Randomized ordering isn't supported by MongoDB.")
 
@@ -218,11 +216,15 @@ def _get_ordering(self):
             if name == "pk":
                 name = opts.pk.name
 
-            try:
-                column = opts.get_field(name).column
-            except FieldDoesNotExist:
-                # `name` is an annotation in $project.
-                column = name
+            if LOOKUP_SEP in order:
+                orderby, _ = self.find_ordering_name(order, self.query.get_meta())[0]
+                column = orderby.expression.as_mql(self, self.connection).removeprefix("$")
+            else:
+                try:
+                    column = opts.get_field(name).column
+                except FieldDoesNotExist:
+                    # `name` is an annotation in $project.
+                    column = name
             column_ordering.append((column, ascending))
         return column_ordering
 

django_mongodb/features.py

@@ -137,6 +137,13 @@ 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",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {
@@ -612,18 +619,6 @@ def django_test_expected_failures(self):
         "Randomized ordering isn't supported by MongoDB.": {
             "ordering.tests.OrderingTests.test_random_ordering",
         },
-        # https://github.com/mongodb-labs/django-mongodb/issues/34
-        "Ordering can't span tables on MongoDB": {
-            "queries.tests.ConditionalTests.test_infinite_loop",
-            "queries.tests.NullableRelOrderingTests.test_join_already_in_query",
-            "queries.tests.Queries1Tests.test_order_by_related_field_transform",
-            "queries.tests.Queries1Tests.test_ticket7181",
-            "queries.tests.Queries1Tests.test_tickets_2076_7256",
-            "queries.tests.Queries1Tests.test_tickets_2874_3002",
-            "queries.tests.Queries5Tests.test_ordering",
-            "queries.tests.Queries5Tests.test_ticket9848",
-            "queries.tests.Ticket14056Tests.test_ticket_14056",
-        },
         "Queries without a collection aren't supported on MongoDB.": {
             "queries.test_q.QCheckTests",
             "queries.test_query.TestQueryNoModel",