[Django] #24849: Broken squashmigration when model related to another one gets deleted
Django
----------------------------+--------------------
Reporter: riklaunim | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
I've got a simple example of an broken squashmigration I had in two apps.
The problem is that if a model gets deleted, that has relation to other
model then the squash will crash as something will want to do some
operation on the non-existing model (relation presence is essential,
tested on postgres):
Initial:
{{{
class Category(models.Model):
title = models.CharField(max_length=100)
class News(models.Model):
title = models.CharField(max_length=100)
category = models.ForeignKey(Category)
}}}
Second migration:
{{{
class Category(models.Model):
title = models.CharField(max_length=100)
class NewCategory(models.Model):
title = models.CharField(max_length=100)
class News(models.Model):
title = models.CharField(max_length=100)
category = models.ForeignKey(NewCategory, blank=True, null=True)
new_category = models.ForeignKey(NewCategory, blank=True, null=True)
}}}
Third:
{{{
class NewCategory(models.Model):
title = models.CharField(max_length=100)
class News(models.Model):
title = models.CharField(max_length=100)
new_category = models.ForeignKey(NewCategory, blank=True, null=True)
}}}
Squash looks like so:
{{{
operations = [
migrations.CreateModel(
name='Category',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('title', models.CharField(max_length=100)),
],
),
migrations.CreateModel(
name='News',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('title', models.CharField(max_length=100)),
('category', models.ForeignKey(blank=True,
to='relateddeleted.Category', null=True)),
],
),
migrations.CreateModel(
name='NewCategory',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('title', models.CharField(max_length=100)),
],
),
migrations.AddField(
model_name='news',
name='new_category',
field=models.ForeignKey(blank=True,
to='relateddeleted.NewCategory', null=True),
),
migrations.RemoveField(
model_name='news',
name='category',
),
migrations.DeleteModel(
name='Category',
),
]
}}}
And on a clean database it throws:
{{{
Applying
relateddeleted.0001_squashed_0003_auto_20150524_2020...Traceback (most
recent call last):
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: relation "relateddeleted_category" does not
exist
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/__init__.py", line 338, in
execute_from_command_line
utility.execute()
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/__init__.py", line 330, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/commands/test.py", line 30, in
run_from_argv
super(Command, self).run_from_argv(argv)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/base.py", line 390, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/commands/test.py", line 74, in execute
super(Command, self).execute(*args, **options)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/base.py", line 441, in execute
output = self.handle(*args, **options)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/commands/test.py", line 90, in handle
failures = test_runner.run_tests(test_labels)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/test/runner.py", line 210, in run_tests
old_config = self.setup_databases()
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/test/runner.py", line 166, in setup_databases
**kwargs
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/test/runner.py", line 370, in setup_databases
serialize=connection.settings_dict.get("TEST", {}).get("SERIALIZE",
True),
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/base/creation.py", line 368, in create_test_db
test_flush=not keepdb,
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/__init__.py", line 120, in call_command
return command.execute(*args, **defaults)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/base.py", line 441, in execute
output = self.handle(*args, **options)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/core/management/commands/migrate.py", line 221, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/migrations/executor.py", line 110, in migrate
self.apply_migration(states[migration], migration, fake=fake,
fake_initial=fake_initial)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/migrations/executor.py", line 147, in apply_migration
state = migration.apply(state, schema_editor)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/base/schema.py", line 91, in __exit__
self.execute(sql)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/base/schema.py", line 111, in execute
cursor.execute(sql, params)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/utils.py", line 97, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/utils/six.py", line 658, in reraise
raise value.with_traceback(tb)
File "/home/piotr/devel/envs/migracje/lib/python3.4/site-
packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "relateddeleted_category" does
not exist
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/24849>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
Reporter: riklaunim | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by timgraham):
* needs_better_patch: => 0
* stage: Unreviewed => Accepted
* needs_tests: => 0
* needs_docs: => 0
Comment:
I had to add `related_name` in step two to avoid a clashing accessor error
from the system check error. With that, when I tried to reproduce this, I
got the following squashed migration:
{{{
operations = [
migrations.CreateModel(
name='News',
fields=[
('id', models.AutoField(primary_key=True, serialize=False,
auto_created=True, verbose_name='ID')),
('title', models.CharField(max_length=100)),
('category', models.ForeignKey(blank=True, null=True,
to='squash.NewCategory', related_name='foo')),
],
),
migrations.CreateModel(
name='NewCategory',
fields=[
('id', models.AutoField(primary_key=True, serialize=False,
auto_created=True, verbose_name='ID')),
('title', models.CharField(max_length=100)),
],
),
migrations.AddField(
model_name='news',
name='new_category',
field=models.ForeignKey(blank=True, null=True,
to='squash.NewCategory'),
),
migrations.RemoveField(
model_name='news',
name='category',
),
]
}}}
This has the problem that `NewCategory` is created after it's used in the
`ForeignKey` which results in `ValueError: Related model
'squash.NewCategory' cannot be resolved` when migrating. Accepting at
least on that basis.
--
Ticket URL: <https://code.djangoproject.com/ticket/24849#comment:1>
Django
Reporter: riklaunim | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by riklaunim):
Looks totally different. Old FK gets null/blank and new FK gets blank/null
from start, then the old one is dropped. Without the need for
related_name.
--
Ticket URL: <https://code.djangoproject.com/ticket/24849#comment:2>
Django
Reporter: riklaunim | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by riklaunim):
Here is my example: https://github.com/riklaunim/django-
examples/tree/master/suqashexamples/relateddeleted/migrations
--
Ticket URL: <https://code.djangoproject.com/ticket/24849#comment:3>
Django
Reporter: riklaunim | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Old description:
New description:
I've got a simple example of an broken squashmigration I had in two apps.
The problem is that if a model gets deleted, that has relation to other
model then the squash will crash as something will want to do some
operation on the non-existing model (relation presence is essential,
tested on postgres):
Initial:
{{{
class Category(models.Model):
title = models.CharField(max_length=100)
class News(models.Model):
title = models.CharField(max_length=100)
category = models.ForeignKey(Category)
}}}
Second migration:
{{{
class Category(models.Model):
title = models.CharField(max_length=100)
class NewCategory(models.Model):
title = models.CharField(max_length=100)
class News(models.Model):
title = models.CharField(max_length=100)
category = models.ForeignKey(Category, blank=True, null=True)
Third:
--
Comment (by timgraham):
There was a typo in the "Second migration" step in the description:
`category = models.ForeignKey(NewCategory, ...` instead of
`ForeignKey(Category ...`. I fixed that and can now reproduce the same
traceback you reported as of a76309f007fff6957f39190b06f8a9055f73130f
(Django 1.10.dev).
--
Ticket URL: <https://code.djangoproject.com/ticket/24849#comment:4>
Django
Reporter: Piotr Maliński | Owner: nobody
Type: Bug | Status: closed
Component: Migrations | Version: 1.8
Severity: Normal | Resolution: fixed
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Jacob Walls):
* status: new => closed
* resolution: => fixed
Comment:
Bisected this one while having a look at the other `squashmigrations`
tickets.
Fixed in b1cbbe926789bcfc2e118c7d7c7a0f30fab5248a. (#25530)
The regression test included appears to cover this case, so I think
closing is appropriate. Let me know if anyone disagrees.
--
Ticket URL: <https://code.djangoproject.com/ticket/24849#comment:5>