add NotSupportedError for update queries that use multiple collections

Author: timgraham

README.md

@@ -113,11 +113,13 @@ Migrations for 'admin':
   - `bulk_update()`
   - `dates()`
   - `datetimes()`
-  - `delete()`, if the query uses multiple collections.
   - `distinct()`
   - `extra()`
   - `prefetch_related()`
 
+- `QuerySet.delete()` and `update()` do not support queries that span multiple
+  collections.
+
 - `Subquery`, `Exists`, and using a `QuerySet` in `QuerySet.annotate()` aren't
   supported.
 

django_mongodb/compiler.py

@@ -377,6 +377,13 @@ def execute_update(self, update_spec, **kwargs):
         options = dict(options, **kwargs)
         return collection.update_many(criteria, update_spec, **options).matched_count
 
+    def check_query(self):
+        super().check_query()
+        if len([a for a in self.query.alias_map if self.query.alias_refcount[a]]) > 1:
+            raise NotSupportedError(
+                "Cannot use QuerySet.update() when querying across multiple collections on MongoDB."
+            )
+
 
 class SQLAggregateCompiler(SQLCompiler):
     pass

django_mongodb/features.py

@@ -83,7 +83,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "ordering.tests.OrderingTests.test_order_by_ptr_field_with_default_ordering_by_expression",
         "queries.tests.Queries1Tests.test_order_by_tables",
         "queries.tests.Queries1Tests.test_ticket4358",
-        "queries.tests.Queries4Tests.test_ticket7095",
         "queries.tests.TestTicket24605.test_ticket_24605",
         "queries.tests.TestInvalidValuesRelation.test_invalid_values",
         # alias().order_by() doesn't work.
@@ -96,8 +95,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # QuerySet.explain() not implemented:
         # https://github.com/mongodb-labs/django-mongodb/issues/28
         "queries.test_explain.ExplainUnsupportedTests.test_message",
-        # 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 = {
@@ -415,6 +412,10 @@ def django_test_expected_failures(self):
             "delete_regress.tests.Ticket19102Tests.test_ticket_19102_select_related",
             "one_to_one.tests.OneToOneTests.test_o2o_primary_key_delete",
         },
+        "Cannot use QuerySet.update() when querying across multiple collections on MongoDB.": {
+            "queries.tests.Queries4Tests.test_ticket7095",
+            "queries.tests.Queries5Tests.test_ticket9848",
+        },
         "QuerySet.dates() is not supported on MongoDB.": {
             "annotations.tests.AliasTests.test_dates_alias",
             "dates.tests.DatesTests.test_dates_trunc_datetime_fields",