implement SchemaEditor.alter_unique_together()

Author: timgraham

django_mongodb/features.py

@@ -85,9 +85,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # AlterField (unique)
         "schema.tests.SchemaTests.test_indexes",
         "schema.tests.SchemaTests.test_unique",
-        # alter_unique_together
-        "migrations.test_operations.OperationTests.test_alter_unique_together",
-        "schema.tests.SchemaTests.test_unique_together",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {

django_mongodb/schema.py

@@ -31,6 +31,9 @@ def _create_model_indexes(self, model):
         # Meta.index_together (RemovedInDjango51Warning)
         for field_names in model._meta.index_together:
             self._add_composed_index(model, field_names)
+        # Meta.unique_together
+        if model._meta.unique_together:
+            self.alter_unique_together(model, [], model._meta.unique_together)
         # Meta.constraints
         for constraint in model._meta.constraints:
             self.add_constraint(model, constraint)
@@ -123,7 +126,28 @@ def alter_index_together(self, model, old_index_together, new_index_together):
             self._add_composed_index(model, field_names)
 
     def alter_unique_together(self, model, old_unique_together, new_unique_together):
-        pass
+        olds = {tuple(fields) for fields in old_unique_together}
+        news = {tuple(fields) for fields in new_unique_together}
+        # Deleted uniques
+        for field_names in olds.difference(news):
+            self._remove_composed_index(
+                model,
+                field_names,
+                {"unique": True, "primary_key": False},
+            )
+        # Created uniques
+        for field_names in news.difference(olds):
+            fields = [model._meta.get_field(field) for field in field_names]
+            name = str(
+                self._unique_constraint_name(
+                    model._meta.db_table, [field.column for field in fields]
+                )
+            )
+            constraint = UniqueConstraint(
+                fields=field_names,
+                name=name,
+            )
+            self.add_constraint(model, constraint)
 
     def add_index(self, model, index, field=None, unique=False):
         if index.contains_expressions: