I have a Django models with a duplicate field name trading I didn't noticed at the time I ran makemigration followed by the migrate command (both commands didn't throw any error). As you can see in the model.py below, the name "trading" is used for a BooleanField and a CharField.
But now I would like to remove or rename one of them and Django throws an error saying:
django.db.utils.DataError: invalid input syntax for type boolean: "future"
I'm not familiar with Postgres SQL and have no clue how to solve this problem without destroying and recreating the databse from scratch.
class Account(models.Model):
exchange = models.ForeignKey(Exchange, on_delete=models.CASCADE, related_name='account', null=True)
strategy = models.ForeignKey(Strategy, on_delete=models.CASCADE, related_name='account', null=True)
limit_order, credentials, trading = [models.BooleanField(default=True) for i in range(3)]
trading = models.CharField(max_length=12, null=True, blank=True, choices=[('future', 'future'),
('swap', 'swap')
])
I've try to first rename the CharField from trading to instrument but in the migration file it looks like Django wants to add a new field. The problem is that everything I modify in my models generate an error. How can I fix this issue while preserving the database?
This is the first migration file that generated the error:
# Generated by Django 3.0.6 on 2020-07-16 10:11
from django.db import migrations, models
class Migration(migrations.Migration):
dependencies = [
('trading', '0011_auto_20200714_0758'),
]
operations = [
migrations.AddField(
model_name='account',
name='instrument',
field=models.CharField(blank=True, choices=[('future', 'future'), ('swap', 'swap')], max_length=12, null=True),
),
migrations.AlterField(
model_name='account',
name='trading',
field=models.BooleanField(default=True),
),
]
Thank you
I answer my own question since I successfully fixed the problem by:
keep the first migration file that caused the problem and removing the others
remove all reference to the duplicate fields in my models
then modify the file as bellow
From :
operations = [
migrations.AddField(
model_name='account',
name='instrument',
field=models.CharField(blank=True, choices=[('future', 'future'), ('swap', 'swap')], max_length=12, null=True),
),
migrations.AlterField(
model_name='account',
name='trading',
field=models.BooleanField(default=True),
),
]
To :
operations = [
migrations.RemoveField(
model_name='account',
name='trading',
),
]
How can I stop Django 2.2.4 from trying to create a database column that already exists when making a model managed?
I have 2 models, ticket and message, which were connected to tables in a third-party database so the models were created with managed=False. I'm moving away from the third-party tool. The ticket model was change to managed=True a while ago by somebody else, and now I'm trying to do the same with the message model.
These are the relevant parts of the model:
from django.db import models
class Message(models.Model):
mid = models.BigAutoField(db_column='MID', primary_key=True)
ticket = models.ForeignKey('Ticket', on_delete=models.CASCADE, db_column='TID')
author = models.CharField(db_column='AUTHOR', max_length=32)
date = models.DateTimeField(db_column='DATE')
internal = models.CharField(db_column='INTERNAL', max_length=1)
isoper = models.CharField(db_column='ISOPER', max_length=1)
headers = models.TextField(db_column='HEADERS')
msg = models.TextField(db_column='MSG')
class Meta:
# managed = False
db_table = 'messages'
permissions = (
("can_change_own_worked_time", "Can change own worked time"),
("can_change_own_recently_worked_time", "Can change own recently worked time"),
("can_change_subordinate_worked_time", "Can change subordinate worked time"),
)
This are the migrations that get generated by commenting out managed=False:
# Generated by Django 2.2.4 on 2020-06-18 20:56 (0017_auto_20200618_1656)
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('troubleticket', '0016_auto_20200511_1644'),
]
operations = [
migrations.AlterModelOptions(
name='message',
options={'permissions': (('can_change_own_worked_time', 'Can change own worked time'), ('can_change_own_recently_worked_time', 'Can change own recently worked time'), ('can_change_subordinate_worked_time', 'Can change subordinate worked time'))},
),
]
# Generated by Django 2.2.4 on 2020-06-18 21:14 (0018_message_ticket)
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
('troubleticket', '0017_auto_20200618_1656'),
]
operations = [
migrations.AddField(
model_name='message',
name='ticket',
field=models.ForeignKey(db_column='TID', default=1, on_delete=django.db.models.deletion.CASCADE, to='troubleticket.Ticket'),
preserve_default=False,
),
]
When I try to apply those migrations I get this error:
django.db.utils.OperationalError: (1060, "Duplicate column name 'TID'")
The initial migration didn't include the TID column and neither do any of the subsequent migrations so I understand why Django thinks it's a new column. But it isn't a new column (the model has had it since the first time it was committed to the git repo) so I also understand why MySQL is throwing an error.
This is the initial migration:
# Generated by Django 2.0.8 on 2018-08-20 14:43 (0001_initial)
from django.db import migrations, models
class Migration(migrations.Migration):
initial = True
dependencies = [
]
operations = [
migrations.CreateModel(
name='Message',
fields=[
('mid', models.BigAutoField(db_column='MID', primary_key=True, serialize=False)),
('author', models.CharField(db_column='AUTHOR', max_length=32)),
('date', models.DateTimeField(db_column='DATE')),
('internal', models.CharField(db_column='INTERNAL', max_length=1)),
('isoper', models.CharField(db_column='ISOPER', max_length=1)),
('headers', models.TextField(db_column='HEADERS')),
('msg', models.TextField(db_column='MSG')),
],
options={
'managed': False,
'db_table': 'messages',
},
),
migrations.CreateModel(
name='Ticket',
fields=[
('id', models.BigIntegerField(db_column='ID', primary_key=True, serialize=False)),
('accesskey', models.CharField(db_column='ACCESSKEY', max_length=64)),
('open', models.DateTimeField(db_column='OPEN')),
('updated', models.DateTimeField(db_column='UPDATED')),
('closed', models.DateTimeField(db_column='CLOSED', null=True)),
('status', models.CharField(db_column='STATUS', max_length=3)),
('oper', models.CharField(db_column='OPER', max_length=32)),
('email', models.CharField(db_column='EMAIL', max_length=128)),
('name', models.CharField(db_column='NAME', max_length=128)),
('subject', models.CharField(db_column='SUBJECT', max_length=255)),
('lname', models.CharField(db_column='LNAME', max_length=50)),
('company', models.CharField(db_column='C0', max_length=255)),
('type', models.CharField(db_column='C1', max_length=255)),
('c2', models.CharField(db_column='C2', max_length=255)),
('c3', models.DecimalField(db_column='C3', decimal_places=2, max_digits=6)),
('c4', models.CharField(db_column='C4', max_length=255)),
('pending', models.CharField(db_column='C5', max_length=255)),
('c6', models.CharField(db_column='C6', max_length=255)),
('c7', models.CharField(db_column='C7', max_length=255)),
('c8', models.CharField(db_column='C8', max_length=255)),
('cc', models.CharField(db_column='C9', max_length=255)),
('grp', models.CharField(db_column='GRP', max_length=10)),
('item', models.CharField(db_column='ITEM', max_length=255)),
],
options={
'managed': False,
'db_table': 'tickets',
},
),
]
2 Seconds after writing my comment I figured out how to solve the problem.
When 'migrating' from another ORM to Django always consider the following aspects.
The following is my recommendation of order, but I'm still learning how to use django migrations, so keep that in mind.
1. Consider which fields of the model are currently known to django
It is important to note, that the actual content of the database does not matter to django when calculating which columns to add or alter. This means that, in the initial migration of the django models, where managed is still =False, the columns are "created" and registered by django. When makemigrations calculates which columns to add, it only takes the columns mentioned in the initial migration as given. Not the actual contents of the db.
Knowing that, we can now go field for field and decide for each one according to point 2.
2. Consider which fields of the model should or should not be created by django
Now, generally, when setting a Model managed=True fields will fall into 3 categories.
2.1 The field is currently in the model definition, the database, and is also in the initial commit.
For this case, no actions need to be taken.
2.2 The field is currently in the model definition, the database, but is not in the initial commit.
For this case, the field definition must be added to the original initial migration script. As such, the migrations.CreateModel call might look like this:
...
('field_already_present', models.FloatField(blank=True, null=True)),
...
2.3 The field is currently in the database, but not in the model definition or the initial commit
If the field is not needed in the django application it can be left out.
If it is needed at some point it will have to be added to the model as well as the first initial migration. That way, django makemigrations will not attempt to create the field.
3. Set managed=True
Now set managed=True and make your migrations. Do so twice! The first time, makemigrations will set the model to managed, then it will add fields not in the initial commit.
After this, the model can be treated same as a normally created and managed-from-the-start django model.
I've got this model in my Django application:
class ClubSession(models.Model):
location = models.CharField(max_length=200)
coach = models.ForeignKey('auth.User', on_delete=models.CASCADE)
date = models.DateTimeField(default=now)
details = models.TextField()
def __str__(self):
return self.title
I can run python manage.py makemigrations club_sessions without issue but when I thn run python manage.py migrate club_sessions I get ValueError: Field 'id' expected a number but got 'username'. username is a superuser and already exists.
How do I resolve this?
This is the latest migration:
# Generated by Django 3.0.6 on 2020-05-28 15:07
from django.conf import settings
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
migrations.swappable_dependency(settings.AUTH_USER_MODEL),
('club_sessions', '0004_auto_20200528_1450'),
]
operations = [
migrations.AlterField(
model_name='clubsession',
name='coach',
field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL),
),
migrations.AlterField(
model_name='clubsession',
name='location',
field=models.CharField(max_length=200),
),
]
By default Django lets a ForeignKey refer to the primary key of the target model. This also has some advantages to make relations more uniform.
If you really want to save the username in the ForeignKey, you can specify a to_field=… parameter [Django-doc] and let it refer to a column that is unique (the username of the default User model is unique), so we can refer to it with:
from django.conf import settings
class ClubSession(models.Model):
location = models.CharField(max_length=200)
coach = models.ForeignKey(
settings.AUTH_USER_MODEL,
on_delete=models.CASCADE,
to_field='username'
)
date = models.DateTimeField(default=now)
details = models.TextField()
def __str__(self):
return self.title
You will need to remove the already existing migration and make a new one in order to migrate the database properly.
Note: It is normally better to make use of the settings.AUTH_USER_MODEL [Django-doc] to refer to the user model, than to use the User model [Django-doc] directly. For more information you can see the referencing the User model section of the documentation.
I have a very similar situation like this: Django migration strategy for renaming a model and relationship fields
I need to rename Foo to Bar.
We have an identical myapp:
class Foo(models.Model):
name = models.CharField(unique=True, max_length=32)
description = models.TextField(null=True, blank=True)
But I have in my myotherapp a ManyToMany field:
class AnotherModel(models.Model):
foo = models.ForeignKey(Foo)
is_awesome = models.BooleanField()
class YetAnotherModel(models.Model):
foo = models.ManyToManyField(Foo, blank=True, null=True) # Here!
is_ridonkulous = models.BooleanField()
I tried rename:
foo = models.ManyToManyField(Foo, blank=True, null=True)
to IntegerField() but doesn't work. How can I do that?
This is how I did it. Note: I was NOT in production, so I did not have to worry about information already in the tables. If you currently have data that you need to keep in the linking table, back up your data first. Also, I was using Django 1.9, but I think that everything referenced here is in 1.8 too.
The issue with the many-to-many relationship is the intermediate tables. Using RemoveField and AddField handled that.
The myapp migration for the model rename probably looks something like this:
class Migration(migrations.Migration):
dependencies = [
('Foo', '0001_initial.py'),
]
operations = [
migrations.RenameModel(
old_name='Foo',
new_name='Bar',
),
]
Next you would run:
python manage.py makemigrations --empty myotherapp
Then you would put this code in the new migration:
dependencies = [
('myotherapp', '0001_initial.py'),
('myapp', '0002_whateverthismigrationwasnamed')
]
operations = [
migrations.RemoveField(
model_name='YetAnotherModel',
name='Foo'
),
migrations.AddField(
model_name='YetAnotherModel',
name='Bar',
field=models.ManyToManyField(blank=True, null=True, to='myapp.Bar'),
),
]
It's important to make sure that you add the rename model migration from myapp as a dependency so it runs first.
Now, if you are in production you should NOT use this method without taking precautions. It straight up deletes the linking table. This from the django docs on RemoveField:
Bear in mind that when reversed, this is actually adding a field to a model. The operation is reversible (apart from any data loss, which of course is irreversible) if the field is nullable or if it has a default value that can be used to populate the recreated column.
If you are in production, you will want to take steps to backup the data so you can restore it into the new table.
I' trying to migrate this model:
class Questionpart_image(models.Model):
questionpart = models.ForeignKey(Questionpart, null=True, blank=True)
image = models.ImageField()
to this:
class Questionpart_image(Questionpart): # notice this base class
image = models.ImageField()
to make advantage of inheritance. Django produces the following migration:
class Migration(migrations.Migration):
dependencies = [
('ochsite', '0016_auto_20150809_1903'),
]
operations = [
migrations.RemoveField(
model_name='questionpart_image',
name='id',
),
migrations.RemoveField(
model_name='questionpart_image',
name='questionpart',
),
migrations.AddField(
model_name='questionpart_image',
name='questionpart_ptr',
field=models.OneToOneField(default='', primary_key=True, to='ochsite.Questionpart', serialize=False, parent_link=True, auto_created=True),
preserve_default=False,
),
]
but this does not set the right foreign key to questionpart_ptr from questionpart field. How can I achieve that?
I've been searching for a long time, but nothing...thanks
Simply don't rely on automatic migrations, make your own or modify that one.
Simplest solution will be by moving AddField in migration to the top of the list and inject between it and RemoveFields RunPython block that will rewrite id's from old field to new (and in other direction in reverse, if needed).