Altering AutoFields with renaming a column crashes on PostgreSQL.

[Benoît Vinot]

Hi, here is my problem. I have an independent table with a id primary key. I would like this table to inherit from a new parent table. I have generated migrations which work with Django version 4.0.7 but fail with Django 4.1.

I have renamed the field id into base_ptr (Base is the new parent table) and then, in another migration file, I try to make this column to be a 1 to 1 column. To do that, I have in my migration an operation like this

        migrations.AlterField(
            model_name="son",
            name="base_ptr",
            field=models.OneToOneField(
                auto_created=True,
                on_delete=django.db.models.deletion.CASCADE,
                parent_link=True,
                primary_key=True,
                serialize=False,
                to="app.Base",
            ),
        ),

which leads to this SQL code

BEGIN;
--
-- Alter field base_ptr on son
--
ALTER TABLE "app_son" RENAME COLUMN "base_ptr" TO "base_ptr_id";
ALTER TABLE "app_son" ALTER COLUMN "base_ptr" DROP IDENTITY IF EXISTS;
ALTER TABLE "app_son" ALTER COLUMN "base_ptr_id" TYPE integer;
DROP SEQUENCE IF EXISTS "app_son_base_ptr_id_seq" CASCADE;
ALTER TABLE "app_son" ADD CONSTRAINT "app_son_base_ptr_id_d3673d48_fk_app_base" FOREIGN KEY ("base_ptr_id") REFERENCES "app_base" ("id") DEFERRABLE INITIALLY DEFERRED;
--

This SQL code fails because the second line (DROP IDENTITY EXISTS) references the base_ptr column which has been renamed into base_ptr_id by the first line...

[Mariusz Felisiak]

Can you provide a sample project to reproduce? This transition is quite tricky.

[Mariusz Felisiak]

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6. We should use the new column name when dropping an identity:

django/db/backends/postgresql/schema.py

@@ -175 +175 @@
                 self.sql_drop_indentity
                 % {
                     "table": self.quote_name(table),
-                    "column": self.quote_name(strip_quotes(old_field.column)),
+                    "column": self.quote_name(strip_quotes(new_field.column)),
                 }
             )
             column = strip_quotes(new_field.column)

Benoît, would you like to prepare a patch? (tests can be tricky.)

[Benoît Vinot]

I have attached the three migrations files of the small example but you were too fast for me...

It would be my first contribution... I can start a PR on GitHub

[Mariusz Felisiak]

Can you confirm the diff works for you?

[Benoît Vinot]

I confirm it works

[Mariusz Felisiak]

Great!, I created a regression test inspired by your migrations:

tests/schema/tests.py

@@ -1588 +1588 @@
         # OneToOneField.
         self.assertEqual(counts, {"fks": expected_fks, "uniques": 1, "indexes": 0})
 
+    def test_autofield_to_o2o(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+            editor.create_model(Note)
+
+        # Rename the field.
+        old_field = Author._meta.get_field("id")
+        new_field = AutoField(primary_key=True)
+        new_field.set_attributes_from_name("note_ptr")
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, old_field, new_field, strict=True)
+        # Alter AutoField to OneToOneField.
+        new_field_o2o = OneToOneField(Note, CASCADE)
+        new_field_o2o.set_attributes_from_name("note_ptr")
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, new_field, new_field_o2o, strict=True)
+        columns = self.column_classes(Author)
+        field_type, _ = columns["note_ptr_id"]
+        self.assertEqual(
+            field_type, connection.features.introspected_field_types["IntegerField"]
+        )
+
     def test_alter_field_fk_keeps_index(self):
         with connection.schema_editor() as editor:
             editor.create_model(Author)

[Mariusz Felisiak]

Replying to Benoît Vinot Roseau Technologies:

It would be my first contribution... I can start a PR on GitHub

Thanks!

[Benoît Vinot]

I have created a PR here with your test and your solution. ​https://github.com/django/django/pull/15964

[Mariusz Felisiak <felisiak.mariusz@…>]

In e3cb8bc:

Fixed #33932 -- Fixed altering AutoFields to OneToOneField on PostgreSQL.

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 85942cf6:

[4.1.x] Fixed #33932 -- Fixed altering AutoFields to OneToOneField on PostgreSQL.

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6.

Backport of e3cb8bcb7d2a2d392e726ee1f7e32a8d9038e14c from main