add helpers to add/delete unique

Author: timgraham

django_mongodb/schema.py

@@ -26,10 +26,7 @@ def _create_model_indexes(self, model):
         # Field uniques
         for field in model._meta.local_fields:
             if field.unique and field.column != "_id":
-                constraint = UniqueConstraint(
-                    fields=[field.name], name=f"{model._meta.db_table}_{field.column}_key"
-                )
-                self.add_constraint(model, constraint)
+                self._add_unique_for_field(model, field)
         # Meta.index_together (RemovedInDjango51Warning)
         for field_names in model._meta.index_together:
             index = Index(fields=field_names)
@@ -66,10 +63,7 @@ def add_field(self, model, field):
         if self._field_should_be_indexed(model, field):
             self._add_index_for_field(model, field)
         if field.unique and field.column != "_id":
-            constraint = UniqueConstraint(
-                fields=[field.name], name=f"{model._meta.db_table}_{field.column}_key"
-            )
-            self.add_constraint(model, constraint, field=field)
+            self._add_unique_for_field(model, field)
 
     def _add_index_for_field(self, model, field):
         new_index = Index(fields=[field.name])
@@ -97,6 +91,30 @@ def _drop_index_for_field(self, model, field):
             # is to look at its name (refs #28053).
             collection.drop_index(index_name)
 
+    def _add_unique_for_field(self, model, field):
+        constraint = UniqueConstraint(
+            fields=[field.name], name=f"{model._meta.db_table}_{field.column}_key"
+        )
+        self.add_constraint(model, constraint, field=field)
+
+    def _drop_unique_for_field(self, model, field, strict):
+        # Find the unique constraint for this field
+        meta_constraint_names = {constraint.name for constraint in model._meta.constraints}
+        constraint_names = self._constraint_names(
+            model,
+            [field.column],
+            unique=True,
+            primary_key=False,
+            exclude=meta_constraint_names,
+        )
+        if strict and len(constraint_names) != 1:
+            raise ValueError(
+                f"Found wrong number ({len(constraint_names)}) of unique "
+                f"constraints for {model._meta.db_table}.{field.column}"
+            )
+        for constraint_name in constraint_names:
+            self.connection.database[model._meta.db_table].drop_index(constraint_name)
+
     def _alter_field(
         self,
         model,
@@ -113,26 +131,7 @@ def _alter_field(
         if old_field.unique and (
             not new_field.unique or self._field_became_primary_key(old_field, new_field)
         ):
-            # Find the unique constraint for this field
-            meta_constraint_names = {constraint.name for constraint in model._meta.constraints}
-            constraint_names = self._constraint_names(
-                model,
-                [old_field.column],
-                unique=True,
-                primary_key=False,
-                exclude=meta_constraint_names,
-            )
-            if strict and len(constraint_names) != 1:
-                raise ValueError(
-                    f"Found wrong number ({len(constraint_names)}) of unique "
-                    f"constraints for {model._meta.db_table}.{old_field.column}"
-                )
-            for constraint_name in constraint_names:
-                constraint = UniqueConstraint(
-                    fields=[old_field.name],
-                    name=constraint_name,
-                )
-                self.remove_constraint(model, constraint)
+            self._drop_unique_for_field(model, old_field, strict)
         # Removed an index? (no strict check, as multiple indexes are possible)
         # Remove indexes if db_index switched to False or a unique constraint
         # will now be used in lieu of an index. The following lines from the
@@ -161,14 +160,8 @@ def _alter_field(
             # Move unique to the new field, if needed.
             if old_field.unique and new_field.unique and new_field.column != "_id":
                 if not old_field.primary_key:
-                    old_constraint = UniqueConstraint(
-                        fields=[old_field.name], name=f"{model._meta.db_table}_{old_field.column}_key"
-                    )
-                    self.remove_constraint(model, old_constraint)
-                new_constraint = UniqueConstraint(
-                    fields=[new_field.name], name=f"{model._meta.db_table}_{new_field.column}_key"
-                )
-                self.add_constraint(model, new_constraint, field=new_field)
+                    self._drop_unique_for_field(model, old_field, strict)
+                self._add_unique_for_field(model, new_field)
         # Replace NULL with the field default if the field and was changed from
         # NULL to NOT NULL.
         if new_field.has_default() and old_field.null and not new_field.null:
@@ -177,10 +170,7 @@ def _alter_field(
             collection.update_many({column: {"$eq": None}}, [{"$set": {column: default}}])
         # Added a unique?
         if self._unique_should_be_added(old_field, new_field):
-            constraint = UniqueConstraint(
-                fields=[new_field.name], name=f"{model._meta.db_table}_{new_field.column}_key"
-            )
-            self.add_constraint(model, constraint, field=new_field)
+            self._add_unique_for_field(model, new_field)
         # Added an index? Add an index if db_index switched to True or a unique
         # constraint will no longer be used in lieu of an index. The following
         # lines from the truth table show all True cases; the rest are False: