#34333: Django migrations adds constraint before adding field
-------------------------------------+-------------------------------------
Reporter: Raphael Beekmann | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 4.1
Severity: Normal | Resolution:
Keywords: migration, | Triage Stage:
constraint, field | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Raphael Beekmann):
* status: closed => new
* resolution: needsinfo =>
Old description:
> Hello,
>
> I have a model, already created through previous migrations, and in a new
> migration I added a new field with a UniqueConstraint.
> The model looks like this (the new field is 'type') :
>
> {{{
> class Model(models.Model):
> name = models.CharField()
> date = models.DateField()
> type = models.ForeignKey(OtherModel)
>
> class Meta:
> constraints = (
> models.UniqueConstraint(fields=('date', 'type'),
> name='unique_date_for_type'),
> )
> }}}
>
> When I run the makemigrations script it adds first the constraint and
> then the new field. That occurs an error when executing the migration :
>
> {{{
> django.core.exceptions.FieldDoesNotExist: DailyTask has no field named
> 'type'
> }}}
>
> I have to manually move the adds of the constraint before the adds of the
> new field in the migration file to make it work.
New description:
Hello,
I have a model, already created through previous migrations, and in a new
migration I added a new field with an UniqueConstraint. The migrations
script try to create the constraint first and then the new field,
resulting an error :
{{{
django.core.exceptions.FieldDoesNotExist: NewModel has no field named
'category'
}}}
To reproduce the bug :
1. Create a project with two models linked together with a One-to-Many
relation and an unique constraint :
{{{
class Type(models.Model):
name = models.CharField(max_length=10)
class Model(models.Model):
name = models.CharField(max_length=10)
type = models.ForeignKey(Type, on_delete=models.SET_NULL, null=True)
date = models.DateField(auto_now=True)
class Meta:
constraints = (
models.UniqueConstraint(fields=('date', 'type'),
name='unique_type_for_date'),
)
}}}
2. Create a migration file with `manage.py makemigrations`
3. Add a new model with another One-to-Many relation and unique
constraint. The models looks like this :
{{{
class Type(models.Model):
name = models.CharField(max_length=10)
class Category(models.Model):
name = models.CharField(max_length=10)
class Model(models.Model):
name = models.CharField(max_length=10)
type = models.ForeignKey(Type, on_delete=models.SET_NULL, null=True)
category = models.ForeignKey(Category, on_delete=models.SET_NULL,
null=True)
date = models.DateField(auto_now=True)
class Meta:
constraints = (
models.UniqueConstraint(fields=('date', 'type'),
name='unique_type_for_date'),
models.UniqueConstraint(fields=('date', 'category'),
name='unique_category_for_date'),
)
}}}
4. Create a new migration file. The order of the migration's steps are
incorrect and the migration crash :
{{{
class Migration(migrations.Migration):
dependencies = [
('app', '0001_initial'),
]
operations = [
migrations.CreateModel(
name='Category',
fields=[
('id', models.BigAutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('name', models.CharField(max_length=10)),
],
),
migrations.AddConstraint(
model_name='model',
constraint=models.UniqueConstraint(fields=('date',
'category'), name='unique_category_for_date'),
),
migrations.AddField(
model_name='model',
name='category',
field=models.ForeignKey(null=True,
on_delete=django.db.models.deletion.SET_NULL, to='app.category'),
),
]
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/34333#comment:2>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/010701864c9ce949-acd76483-19f6-410b-9218-30967f0447f4-000000%40eu-central-1.amazonses.com.
