I have a simple view on the DB which selects from other DB's tables located on the same MSSQL Server to ultimately serve the collected info as a dropdown to the user.
So far I've added the Model with inspectdb:
class AutPricePlanView(models.Model):
priceplan_name = models.CharField(db_column='PricePlan', max_length=50, blank=True, unique=True)
class Meta:
managed = False # Created from a view. Don't remove.
db_table = 'AUT_PricePlanView'
Also I have a second existing (Django Native) Model where I want to use the values from the view for a Dropdown Field (to keep everything in sync):
class PricePlanDownload(models.Model):
requesting_user = models.CharField(blank=True, default=None, max_length=50, null=True)
requested_at = models.DateTimeField(auto_now_add=True)
document = models.FileField(upload_to='documents/price_plan_uploads/%Y/%m/%d', blank=True)
priceplan = models.ForeignKey(AutPricePlanView, null=True, on_delete=models.DO_NOTHING)
Makemigrations works fine but when I try to actually migrate I get the following issue: (shortened it a little bit)
django.db.utils.ProgrammingError: ('42000', "[42000] [FreeTDS][SQL Server]Foreign key references object 'AUT_PricePlanView' which is not a user table. (1768) (SQLExecDirectW)")
I would be really grateful if someone had an idea or a workaround since I can't figure out what the heck this has to do with a "user" table...
Since the view is not actually a table, you cannot set Foreign Key constraints. Since ForeignKey's default db_constraint value is True, Django tries to set Foreign Key constraints when performing migrations. This is the reason the migration fails.
So, you can turn off the db_constraint option. And you can remove the existing migration file, and re-create the migration file. Then, the migration will success and you can keep everything in sync.
class PricePlanDownload(models.Model):
... other fields ...
priceplan = models.ForeignKey(AutPricePlanView, null=True, on_delete=models.DO_NOTHING, db_constraint=False)
Pro Tip: You can review migration's SQL using python manage.py sqlmigrate <appname> <migration number>, like python manage.py sqlmigrate yourapp 0002.
Update: You can define __str__ to display the correct value at the dropdown menu.
class AutPricePlanView(models.Model):
priceplan_name = models.CharField(db_column='PricePlan', max_length=50, blank=True, unique=True, primary_key=True)
# null=False by default. See https://github.com/django/django/blob/master/django/db/models/fields/__init__.py#L132
def __str__(self):
return self.priceplan_name
class Meta:
managed = False # Created from a view. Don't remove.
db_table = 'AUT_PricePlanView'
I have models and there was no Boolean field in the very beginning when i run makemigraiton and migrate
In that mean time, i added some post...
later i added new field called is_printable as boolean field...
this is my current models:
from django.db import models
import datetime
from django.utils import timezone
Create your models here.
class Article(models.Model):
title = models.CharField(max_length=50)
body = models.TextField()
category = models.CharField(
null=False,
blank=False,
max_length=50,
)
is_printable = models.BooleanField()
date = models.DateTimeField(timezone.now)
when i add
is_printable = models.BooleanField()
I cant run migrate command, it throws me an error called
django.core.exceptions.ValidationError: ["'2019-07-07 06:56:52.693378+00:00' value must be either True or False."]
What is possible solution for this?
When you added is_printable field and ran makemigrations Django would've asked you to enter default value for the newly added field, what is the default value you gave? I presume you gave timezone.now() and because of that it would've thrown error during migrate.
I'm working with a project with docker-compose, where I have a postgre container.
When I run:
docker-compose -f dev.yml run django python manage.py migrate
I get the error:
django.db.utils.ProgrammingError: multiple default values specified for column "id" of table "scrapy_scrapy"
That is happening before I made some changes to my models.py file. But now the file is correct and should be working. This is the content of the models.py file:
from django.db import models
import django
# Create your models here.
class Scrapy(models.Model):
user = models.CharField(max_length=50,blank=True)
password = models.CharField(max_length=50,blank=True)
projecte = models.CharField(max_length=100)
estat_last_check = models.CharField(max_length=700, default="", blank=True)
date = models.DateTimeField(default=django.utils.timezone.now, blank=True)
app_label = ''
def __str__(self): # __unicode__ on Python 2
return self.projecte + " - " + self.user
class Meta:
app_label = 'scrapy'
As you can see, no id filed is defined anymore, so, why is complaining about that field?
I've done my research and tried some possible solutions, but no luck. I've already tried deleting the full Docker container and creating it again, or trying to delete the database.
Any ideas?
I have below model:
class Property(models.Model):
job = models.ForeignKey(Job, on_delete=models.CASCADE)
app = models.ForeignKey(App, on_delete=models.CASCADE)
name = models.CharField(max_length=120)
value = models.CharField(max_length=350, blank=True)
description = models.TextField(blank=True)
pub_date = models.DateTimeField('date_published', default=timezone.now)
class Meta:
verbose_name_plural = "properties"
unique_together = (('value', 'name'),)
def __str__(self):
return self.name
When I try to create a Property object in admin page (I'm using Django Suit) with name/value which are already exist I get the exception: "Property with this Value and Name already exists." So it works perfect.
But in manage.py shell:
>>>from myapp.models import App, Property, Job
>>>from django.shortcuts import get_object_or_404
>>>app = get_object_or_404(App, app_name='BLABLA')
>>>job = get_object_or_404(Job, job_name='BLABLA2')
>>> Property.objects.create(job=job, app=app, name='1', value='1')
<Property: 1>
>>> Property.objects.create(job=job, app=app, name='1', value='1')
<Property: 1>
In this case I do not get any exceptions and objects are added in database.
I tried makemigrations, migrate and migrate --run-syncdb.
Django 1.9.12, sqlite3
The unique constraints are enforced at database level. You're not getting any error probably because SQLite doesn't support this type of constraint. You cannot add constraint to existing table in SQLite. If you're in early development stage, drop the table and recreate it with updated constraints. Then it should work fine in shell.
Check SQLite alter table docs for allowed updates on an existing table.
The admin form throws error because it checks uniqueness by itself without relying on database constraints.
I'm trying to modify a M2M field to a ForeignKey field. The command validate shows me no issues and when I run syncdb :
ValueError: Cannot alter field xxx into yyy they are not compatible types (you cannot alter to or from M2M fields, or add or remove through= on M2M fields)
So I can't make the migration.
class InstituteStaff(Person):
user = models.OneToOneField(User, blank=True, null=True)
investigation_area = models.ManyToManyField(InvestigationArea, blank=True,)
investigation_group = models.ManyToManyField(InvestigationGroup, blank=True)
council_group = models.ForeignKey(CouncilGroup, null=True, blank=True)
#profiles = models.ManyToManyField(Profiles, null = True, blank = True)
profiles = models.ForeignKey(Profiles, null = True, blank = True)
Any suggestions?
I stumbled upon this and although I didn't care about my data much, I still didn't want to delete the whole DB. So I opened the migration file and changed the AlterField() command to a RemoveField() and an AddField() command that worked well. I lost my data on the specific field, but nothing else.
I.e.
migrations.AlterField(
model_name='player',
name='teams',
field=models.ManyToManyField(related_name='players', through='players.TeamPlayer', to='players.Team'),
),
to
migrations.RemoveField(
model_name='player',
name='teams',
),
migrations.AddField(
model_name='player',
name='teams',
field=models.ManyToManyField(related_name='players', through='players.TeamPlayer', to='players.Team'),
),
NO DATA LOSS EXAMPLE
I would say: If machine cannot do something for us, then let's help it!
Because the problem that OP put here can have multiple mutations, I will try to explain how to struggle with that kind of problem in a simple way.
Let's assume we have a model (in the app called users) like this:
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person)
def __str__(self):
return self.name
but after some while we need to add a date of a member join. So we want this:
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person, through='Membership') # <-- through model
def __str__(self):
return self.name
# and through Model itself
class Membership(models.Model):
person = models.ForeignKey(Person, on_delete=models.CASCADE)
group = models.ForeignKey(Group, on_delete=models.CASCADE)
date_joined = models.DateField()
Now, normally you will hit the same problem as OP wrote. To solve it, follow these steps:
start from this point:
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person)
def __str__(self):
return self.name
create through model and run python manage.py makemigrations (but don't put through property in the Group.members field yet):
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person) # <-- no through property yet!
def __str__(self):
return self.name
class Membership(models.Model): # <--- through model
person = models.ForeignKey(Person, on_delete=models.CASCADE)
group = models.ForeignKey(Group, on_delete=models.CASCADE)
date_joined = models.DateField()
create an empty migration using python manage.py makemigrations users --empty command and create conversion script in python (more about the python migrations here) which creates new relations (Membership) for an old field (Group.members). It could look like this:
# Generated by Django A.B on YYYY-MM-DD HH:MM
import datetime
from django.db import migrations
def create_through_relations(apps, schema_editor):
Group = apps.get_model('users', 'Group')
Membership = apps.get_model('users', 'Membership')
for group in Group.objects.all():
for member in group.members.all():
Membership(
person=member,
group=group,
date_joined=datetime.date.today()
).save()
class Migration(migrations.Migration):
dependencies = [
('myapp', '0005_create_models'),
]
operations = [
migrations.RunPython(create_through_relations, reverse_code=migrations.RunPython.noop),
]
remove members field in the Group model and run python manage.py makemigrations, so our Group will look like this:
class Group(models.Model):
name = models.CharField(max_length=128)
add members field the the Group model, but now with through property and run python manage.py makemigrations:
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person, through='Membership')
and that's it!
Now you need to change creation of members in a new way in your code - by through model. More about here.
You can also optionally tidy it up, by squashing these migrations.
Potential workarounds:
Create a new field with the ForeignKey relationship called profiles1 and DO NOT modify profiles. Make and run the migration. You might need a related_name parameter to prevent conflicts. Do a subsequent migration that drops the original field. Then do another migration that renames profiles1 back to profiles. Obviously, you won't have data in the new ForeignKey field.
Write a custom migration: https://docs.djangoproject.com/en/1.7/ref/migration-operations/
You might want to use makemigration and migration rather than syncdb.
Does your InstituteStaff have data that you want to retain?
If you're still developing the application, and don't need to preserve your existing data, you can get around this issue by doing the following:
Delete and re-create the db.
go to your project/app/migrations folder
Delete everything in that folder with the exception of the init.py file. Make sure you also delete the pycache dir.
Run syncdb, makemigrations, and migrate.
Another approach that worked for me:
Delete the existing M2M field and run migrations.
Add the FK field and run migrations again.
FK field added in this case has no relation to the previously used M2M field and hence should not create any problems.
This link helps you resolve all problems related to this
The one which worked for me is python3 backend/manage.py migrate --fake "app_name"
I literally had the same error for days and i had tried everything i saw here but still didn'y work.
This is what worked for me:
I deleted all the files in migrations folder exceps init.py
I also deleted my database in my case it was the preinstalled db.sqlite3
After this, i wrote my models from the scratch, although i didn't change anything but i did write it again.
Apply migrations then on the models and this time it worked and no errors.
This worked for Me as well
Delete last migrations
run command python manage.py migrate --fake <application name>
run command 'python manage.py makemigrations '
run command 'python manage.py migrate'
Hope this will solve your problem with deleting database/migrations
First delete the migrations in your app (the folders/ files under 'migrations'
folder)
Showing the 'migrations' folder
Then delete the 'db.sqlite3' file
Showing the 'db.sqlite3' file
And run python manage.py makemigrations name_of_app
Finally run python manage.py migrate
I had the same problem and found this How to Migrate a ‘through’ to a many to many relation in Django article which is really really helped me to solve this problem. Please have a look. I'll summarize his answer here,
There is three model and one(CollectionProduct) is going to connect as many-to-many relationship.
This is the final output,
class Product(models.Model):
pass
class Collection(models.Model):
products = models.ManyToManyField(
Product,
blank=True,
related_name="collections",
through="CollectionProduct",
through_fields=["collection", "product"],
)
class CollectionProduct(models.Model):
collection = models.ForeignKey(Collection, on_delete=models.CASCADE)
product = models.ForeignKey(Product, on_delete=models.CASCADE)
class Meta:
db_table = "product_collection_products"
and here is the solution,
The solution
Take your app label (the package name, e.g. ‘product’) and your M2M field name, and combine them together with and underscore:
APPLABEL + _ + M2M TABLE NAME + _ + M2M FIELD NAME
For example in our case, it’s this:
product_collection_products
This is your M2M’s through database table name. Now you need to edit your M2M’s through model to this:
Also found another solution in In Django you cannot add or remove through= on M2M fields article which is going to edit migration files. I didn't try this, but have a look if you don't have any other solution.
this happens when adding 'through' attribute to an existing M2M field:
as M2M fields are by default handled by model they are defined in (if through is set).
although when through is set to new model the M2M field is handled by that new model, hence the error in alter
solutions:-
you can reset db or
remove those m2m fields and run migration as explained above then create them again
*IF YOU ARE IN THE INITIAL STAGES OF DEVELOPMENT AND CAN AFFORD TO LOOSE DATA :)
delete all the migration files except init.py
then apply the migrations.
python manage.py makemigrations
python manage.py migrate
this will create new tables.