CODEWITHSUNDEEP
djangodjango-migrationsdjango-managers
mdalp
mdalp

Reputation: 77

How to use default manager in django migrations with inherited models?

I have a model Baz that's inheriting from an abstract model Bar which is inheriting as well from an other abstract model Foo.

from django.db import models


class BarManager(models.Manager):
    pass


class Foo(models.Model):
    attr1 = models.CharField(max_length=20)

    objects = models.Manager()

    class Meta:
        abstract = True


class Bar(Foo):
    attr2 = models.CharField(max_length=20)
    bar_objects = BarManager()

    class Meta:
        abstract = True


class Baz(Bar):
    attr3 = models.CharField(max_length=20)

when running a data migration I want to be able to use the default manager Baz.objects:

# Generated by Django 3.0.7 on 2020-06-23 15:57

from django.db import migrations


def update_forward(apps, schema_editor):
    Baz = apps.get_model('migration_manager', 'Baz')
    Baz.objects.filter(attr1='bar').update(attr1='baz')


class Migration(migrations.Migration):

    dependencies = [
        ('migration_manager', '0001_initial'),
    ]

    operations = [
        migrations.RunPython(update_forward),
    ]

but it's not available as I'm getting:

  File "/home/user/code/django_issues/migration_manager/migrations/0002_update_content.py", line 8, in update_forward
    Baz.objects.filter(attr1='bar').update(attr1='baz')
AttributeError: type object 'Baz' has no attribute 'objects'

This is the initial migration that gets created automatically

# Generated by Django 3.0.7 on 2020-06-23 16:13

from django.db import migrations, models
import django.db.models.manager


class Migration(migrations.Migration):

    initial = True

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Baz',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('attr1', models.CharField(max_length=20)),
                ('attr2', models.CharField(max_length=20)),
                ('attr3', models.CharField(max_length=20)),
            ],
            options={
                'abstract': False,
            },
            managers=[
                ('bar_objects', django.db.models.manager.Manager()),
            ],
        ),
    ]

in there there is the managers section which is explicitly making available only the custom model of the parent.

Does anyone have an idea if it's me doing something wrong or it's an issue with django?

I'm on:

Thanks in advance

Upvotes: 0

Views: 689

Answers (1)

JPG
JPG

Reputation: 88499

Use Model._default_manager as

Baz._default_manager

Full example:

def update_forward(apps, schema_editor):
    Baz = apps.get_model('migration_manager', 'Baz')
    Baz._default_manager.filter(attr1='bar').update(attr1='baz')

Upvotes: 1

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