fix QuerySet.update() with multi-table inheritance

Author: timgraham

django_mongodb/compiler.py

@@ -324,8 +324,14 @@ def check_query(self):
             )
 
 
-class SQLUpdateCompiler(SQLCompiler):
+class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler):
     def execute_sql(self, result_type):
+        """
+        Execute the specified update. Return the number of rows affected by
+        the primary update query. The "primary update query" is the first
+        non-empty query that is executed. Row counts for any subsequent,
+        related queries are not available.
+        """
         self.pre_sql_setup()
         values = []
         for field, _, value in self.query.values:
@@ -340,7 +346,14 @@ def execute_sql(self, result_type):
                     )
             prepared = field.get_db_prep_save(value, connection=self.connection)
             values.append((field, prepared))
-        return self.update(values)
+        is_empty = not bool(values)
+        rows = 0 if is_empty else self.update(values)
+        for query in self.query.get_related_updates():
+            aux_rows = query.get_compiler(self.using).execute_sql(result_type)
+            if is_empty and aux_rows:
+                rows = aux_rows
+                is_empty = False
+        return rows
 
     def update(self, values):
         spec = {}

django_mongodb/features.py

@@ -51,9 +51,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "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",
-        # pymongo: ValueError: update cannot be empty
-        "update.tests.SimpleTest.test_empty_update_with_inheritance",
-        "update.tests.SimpleTest.test_nonempty_update_with_inheritance",
         # Pattern lookups that use regexMatch don't work on JSONField:
         # Unsupported conversion from array to string in $convert
         "model_fields.test_jsonfield.TestQuerying.test_icontains",