Primary keys added in non-initial migration are not created as identity columns in PostgreSQL

[jackcbrown89]

In this example, a model was created initially with a primary key on a one-to-one field. The primary key was then moved to a new AutoField. This was working prior to the 4.1 release.

## models.py
class Example(models.Model):
    old_id = models.OneToOneField(
        OtherModel,
        on_delete=models.CASCADE,
        ## primary_key=True,  <--- used to be the primary key
    )

    id = models.AutoField(primary_key=True) # <--- new primary key

Running sqlmigrate on the migration where the primary key changes reveals that the "id" column does not autogenerate values:

$ python manage.py sqlmigrate example 0002

BEGIN;
--
-- Add field id to example
--
ALTER TABLE "example" ADD COLUMN "id" integer NOT NULL PRIMARY KEY;
--
-- Alter field old_id on example
--
ALTER TABLE "example" ALTER COLUMN "old_id" DROP NOT NULL;

When it should be

$ python manage.py sqlmigrate example 0002

BEGIN;
--
-- Add field id to example
--
ALTER TABLE "example" ADD COLUMN "id" integer NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY;
--
-- Alter field old_id on example
--
ALTER TABLE "example" ALTER COLUMN "old_id" DROP NOT NULL;

This seems to be related to the changes made here: https://code.djangoproject.com/ticket/30511
PR: ​https://github.com/django/django/pull/15542

[Mariusz Felisiak]

Thanks for the report! Column suffixes (as GENERATED BY...) should be used when adding a new field:

django/db/backends/base/schema.py

@@ -637 +637 @@
         # It might not actually have a column behind it
         if definition is None:
             return
+        col_type_suffix = field.db_type_suffix(connection=self.connection)
+        if col_type_suffix:
+            definition += f" {col_type_suffix}"
         # Check constraints can go on the column SQL here
         db_params = field.db_parameters(connection=self.connection)
         if db_params["check"]:

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6.

[Mariusz Felisiak]

​PR

[GitHub <noreply@…>]

In 5c803bc:

Fixed #33919 -- Fixed adding AutoFields on PostgreSQL.

Thanks Jack Calvin Brown for the report.

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 3848475e:

[4.1.x] Fixed #33919 -- Fixed adding AutoFields on PostgreSQL.

Thanks Jack Calvin Brown for the report.

Regression in 2eea361eff58dd98c409c5227064b901f41bd0d6.
Backport of 5c803bc0702511c8bc05e9db600367a465514f82 from main