Migration changing db_table and managed not creating new table

[Eduardo Klein]

I had a model like this:

class Decoupe(models.Model):
    constante = models.IntegerField()

    class Meta:
        managed = False
        db_table = "Decoupe"

I ran the first migration and it recognized the options as expected.
Then I removed the meta options, so the model looked like this:

class Decoupe(models.Model):
    constante = models.IntegerField()

I ran make migrations and it created the following:

migrations.AlterModelOptions(
    name='decoupe',
    options={},
),

When I applied it, nothing really happened and of course, when, trying from the shell, to to Decoupe.objects.all(), I got an error saying that the table "myapp_decoupe" did not exits.

I would expect either the table to be renamed or at least created empty.

I tried to workaround this replacing the migrations above with

migrations.DeleteModel("decoupe"),
migrations.CreateModel( ... ),

But when I ran it, I got a error:
RuntimeError: Error creating new content types. Please make sure contenttypes is migrated before trying to migrate apps individually., although the contenttypes is migrated.

Is this a bug or desired behavior since the model was "managed=False"?

[Eduardo Klein]

Sorry, I was in django 1.7.

I also tried removing the "managed=False" from the initial migration and got the same contenttype error. I did not understand why, since I was not changing any content type.

I upgraded then to 1.8. The automatically generated migration was the same and applying it did not change a thing, so I think there is still an issue. Trying to delete and re-create the model as above raised the same error.

What did work was removing the "managed=False" from the initial migration. Django then renamed the table as expected.

Is it intended behavior that any model marked as "managed=False" should never be changed with django's migration?

[Tim Graham]

If managed=False then you're saying that the table already exists, so I don't think changing it to managed=True should issue a CREATE TABLE. The contenttypes error is probably triggered because the table doesn't exist. Can you try doing it in two steps: remove managed=False, run makemigrations, then remove db_table and run makemigrations.

[Eduardo Klein]

Thanks for your quick response.
Doing it in 2 steps worked in django 1.8 (I did not test in django 1.7).

Regarding the contenttype issue, the table (and the model) did exist. This issue does not appear in Django 1.8 anymore, so I'm not sure it's worth digging further.

Maybe it's worth mentioning in the docs that changing a model from the managed=False state to managed=True and making other changes should be done in 2 steps, as you suggested.

Thanks again.

[Tim Graham]

​PR

[GitHub <noreply@…>]

In 80c03b06:

Fixed #24650 -- Documented how to change an unmanaged model to managed.

[Tim Graham <timograham@…>]

In 6be255a2:

[1.10.x] Fixed #24650 -- Documented how to change an unmanaged model to managed.

Backport of 80c03b06ad1461c1a07091806dc0414a4e98905e from master