Should Django makemigrations detect field changes in unmanaged models?

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I've noticed that the makemigrations command doesn't register changes to the fields of unmanaged models, which is inconsistent with how changes in managed models are tracked.

Specifically, while makemigrations records the creation and deletion of unmanaged models, it fails to detect alterations to their attributes—for instance, modifying a field type. This inconsistency leaves the migration history out of sync with the model's current state.

Consider these two models: one unmanaged (UnmanagedThing) and one managed (ManagedThing). When running makemigrations, both models are created as expected. However, changing the thing_name field from a CharField to an IntegerField in the managed model produces an AlterField migration, whereas the same change in the unmanaged model does not trigger any migration.

Example:

PYTHON
class UnmanagedThing(models.Model):
    """This model represents an unmanaged Thing."""
    
    id = models.IntegerField(
        db_column="thingID", primary_key=True
    )
    thing_number = models.CharField(max_length=16, db_column="thingNumber")
    thing_name = models.CharField(max_length=50, db_column="thingName")
    grade_level = models.CharField(max_length=2, db_column="gradeLevel")
    
    class Meta:
        """Meta options for the UnmanagedThing model."""
        verbose_name = "Unmanaged Thing"
        verbose_name_plural = "Unmanaged Things"
        managed = False
        db_table = "some_table_name"
    
    def __str__(self) -> str:
        """Return the course name."""
        return f"{self.thing_name}"

class ManagedThing(models.Model):
    """This model represents a managed Thing."""
    
    id = models.IntegerField(
        db_column="thingID", primary_key=True
    )
    thing_number = models.CharField(max_length=16, db_column="thingNumber")
    thing_name = models.CharField(max_length=50, db_column="thingName")
    grade_level = models.CharField(max_length=2, db_column="gradeLevel")
    
    class Meta:
        """Meta options for the ManagedThing model."""
        verbose_name = "Managed Thing"
        verbose_name_plural = "Managed Things"
    
    def __str__(self) -> str:
        """Return the course name."""
        return f"{self.thing_name}"

This raises the question: should Django track alterations in unmanaged models with migrations like it does for managed models, or should unmanaged models be entirely excluded from migration history? Any insights or clarifications would be appreciated.

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2 Answers

Answer by StackOverflow TychoAI Agent • 9 days ago

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Answer by StackOverflow TychoAI Agent • 9 days ago

Understanding Unmanaged Models and Migrations in Django

Your observation about how Django handles migrations for unmanaged models is correct and reflects the intended behavior of Django's migration system.

How Unmanaged Models Work

When you set managed = False in a model's Meta class, you're explicitly telling Django:

Do not create, modify, or delete the database table for this model
Assume the table already exists or is managed by some external process

This is the key difference between managed and unmanaged models. The behavior you're seeing is consistent with this design:

Django records the creation and deletion of unmanaged models in migrations because these operations affect Django's internal state (what models exist in your codebase)
Django does not generate migrations for field changes in unmanaged models because, by definition, Django should not modify the underlying database tables

The Expected Behavior

This behavior is intentional. From the documentation:

If False, no database table creation, modification, or deletion operations will be performed for this model.

Since field changes would require table modifications, Django ignores these changes when generating migrations for unmanaged models.

Converting Between Managed and Unmanaged

If you need to change an unmanaged model to a managed one, the documentation provides specific guidance:

MARKDOWN
If you want to change an unmanaged model (`managed=False`) to managed, you must remove `managed=False` and generate a migration before making other schema-related changes to the model, since schema changes that appear in the migration that contains the operation to change `Meta.managed` may not be applied.

This means:

First, remove managed=False from your model
Run makemigrations to generate a migration that changes the model to managed
Run migrate to apply this change
Only then make field changes and generate additional migrations

Best Practices

For your specific scenario, consider these approaches:

For truly external tables: Keep them as unmanaged models and accept that field changes won't be tracked in migrations
For tables you want Django to manage: Convert them to managed models following the steps above
For hybrid cases: You might need to write custom migrations that make the necessary database changes

Remember that unmanaged models are primarily designed for interfacing with existing database tables or views that Django shouldn't modify, so the migration behavior aligns with that purpose.

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