I have to work with a legacy database and have the following problem.
My model has a foreign key to the User Model:
class History(models.Model):
uid = models.ForeignKey(User, to_field='username', db_column='uid')
That seems to work.
The Problem is that for some History entries the User entry doesn't exist anymore.
Is there an easy solution?
The Application seems to work fine with it. The only problem is in the Admin-Interface of the Model:
class HistoryAmdin(admin.ModelAdmin):
list_display = ('id', 'uid')
It shows only entries with a valid foreign key.
Is it possible to show also the other entries?
Set you null=True inside your History class.
class History(models.Model):
uid = models.ForeignKey(User, to_field='username', db_column='uid', null=True)
Related
I have a model OrderPage which is manytomany to Site. In Django admin, I want to restrict the selection of sites(Sites which belong to existing OrderPage can not be selected again). Can I do it with unique_together ? I get an error with following model ManyToManyFields are not supported in unique_together
class OrderPage(models.Model):
description = models.CharField(max_length=255, blank=False)
sites = models.ManyToManyField(Site)
class Meta:
unique_together = (('id', 'sites'),)
class Order(models.Model):
order_page = models.ForeignKey(OrderPage)
class OrderPageAdmin(admin.ModelAdmin):
filter_horizontal = ('sites',)
admin.site.register(OrderPage, OrderPageAdmin)
If an Site can have only one OrderPage, you don't need to worry about unique_together.
Ideally you should subclass Site and use a ForeignKey from that to OrderPage. That would natively give you what you're looking for: each site would be able to have one OrderPage, and each OrderPage multiple Sites. This would be the cleanest but you would have to use your subclass throughout the program in place of the original Site which might be more work than you want right now.
class BetterSite(Site):
order_page = models.ForeignKey('OrderPage')
The dirtier way is to keep your M2M and just set the site as unique, since there should only ever be one entry on each site in the M2M table. You would use a 'through' table so you could set the custom uniqueness value:
class OrderPage(models.Model):
description = models.CharField(max_length=255, blank=False)
sites = models.ManyToManyField(Site, through='OrderPageToSite')
class OrderPageToSite(models.Model):
order_page = models.ForeignKey(OrderPage)
site = models.ForeignKey(Site, unique=True)
(Note that I've left these simple but in your FK fields you should also consider setting on_delete and related_name)
As can be seen below, I have 2 models connected via an intermediary model to form a ManyToMany relationship. The problem is that, when I delete a Tender object in get this error.
update or delete on table "tender_details_tender" violates foreign key constraint "user_account_company_tender_id_984ea78c_fk_tender_de" on table "user_account_companyprofile_assignedTenders"
DETAIL: Key (id)=(1) is still referenced from table "user_account_companyprofile_assignedTenders".
I thought by adding on_delete=models.CASCADE in the ForeighKeys (i.e. in the intermediary model) would solve this problem, but apparently not.
class CompanyProfile(models.Model):
assignedTenders = models.ManyToManyField(Tender, through='UsersTenders', related_name='UserCompanies')
# connects users to the tenders they match.
class UsersTenders(models.Model):
user = models.ForeignKey(CompanyProfile, on_delete=models.CASCADE, related_name='userTenderLink')
tender = models.ForeignKey(Tender, on_delete=models.CASCADE, related_name='userTenderLink')
sent = models.BooleanField(default=False, blank=False)
class Meta:
unique_together = ("user", "tender")
class Tender(models.Model):
tenderCategory = models.ManyToManyField(Category, blank=False) #this field holds the tender category, e.g. construction, engineering, human resources etc.
tenderProvince = models.ManyToManyField(Province, blank=False) #this is the province the tender was a
For what its worth, I know what is causing this problem, what I don't know is how to fix it. The problem is that initially I had the ManyToManyField under the CompanyProfile model without the "through" argument, so as you might imagine Django created it's own intermediary table which is "user_account_companyprofile_assignedTenders" as shown in the error. I later decided to create my own intermediary model (i.e. UsersTenders) because I wanted an extra field there, so I had to add the "through" argument in my ManyToManyField (i.e. 'assignedTenders'). That worked fine but the old intermediary model "user_account_companyprofile_assignedTenders" did not get deleted automatically, I assume its because a few relationship had be created before the change. How can I delete "user_account_companyprofile_assignedTenders" without destabilizing my project.
Did you add on_delete after database migration? If so have you made a migration after adding on_delete?
You could try to set null=True to all fields and then try ti figure out which foreign key is causing problems.
bdw. when you set blank=True that only means that your form fields will not insist on this fields to be filled for submitting.
I am working on the project using django 1.9.
I need to add a field to the user model 'Auth_user' table, the field which i want can be another primary key and act here as foreign key in the 'auth_user'.
I searched a lot but fails. Can any buddy provide me some example how to achieve this like how to to add fields to 'auth_user'
You can substitute the user model entirely as described in doc. Here is an example:
AUTH_USER_MODEL = 'myapp.MyUser'
to your settings.py, and add following to your model:
from django.contrib.auth.models import AbstractUser
class MyUser(AbstractUser):
another_object = models.ForeignKey(OtherModel..
just make a new moel with a user foreign key
class Post (models.Model):
title = models.CharField(max_length=80)
slug= models.SlugField(unique=True)
content = models.TextField()
user_creator = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
there you can use as primary key the id of the post, or the slug (unique), and it can be linked to a user, if you need one to one relationship see this or many to many relationship see this
Maybe you just need to extend de model user
https://docs.djangoproject.com/en/1.11/topics/auth/customizing/#extending-the-existing-user-model
I have found in internet different examples on how to handle m2m relations with existing DB models, such as ex1 or here ex2, however I'm still not able to solve the error I get.
My models are depicted below. Basically, all the tables where created manually.
I got the following error message:
OperationalError: (1054, "Unknown column 'supervisor_project.id' in 'field list'").
I'm still a bit confused on when to use unique_together with through. Do you see any errors in the model below? The table supervisor_project has no id field and its PK is composed actually of two FK's, i.e. surrogate PK.
class Supervisor(models.Model):
name = models.CharField(max_length=45, blank=True, null=True, help_text="Name, e.g. John Smith")
class Meta:
managed = False
db_table = 'supervisor'
def __unicode__(self):
return self.name
class Project(models.Model):
title = models.CharField(max_length=45, blank=True, null=True)
supervisors = models.ManyToManyField(Supervisor, through='SupervisorProject', through_fields=('project', 'supervisor'))
class SupervisorProject(models.Model):
supervisor = models.ForeignKey('Supervisor', on_delete=models.CASCADE)
project = models.ForeignKey('Project', on_delete=models.CASCADE)
class Meta:
managed = False
db_table = 'supervisor_project'
unique_together = (('supervisor', 'project'),)
Django requires each model to have exactly one primary key field. It doesn't support multiple-column primary keys yet.
Since you haven't explicitly defined a primary key on the SupervisorProject model, Django assumes that there is an automatic primary key field id. When it includes the id field in a query, you get the error because it doesn't exist.
If possible, I would add an auto-incrementing id column to each intermediate table. There isn't a way to get Django to add the column to the tables automatically. You have set managed=False, so Django expects you to manage the database table.
I have just begun to play around with Django admin views, and to start off, I am trying to do something very simple: showing several fields in the listing of objects using list_display as explained here: https://docs.djangoproject.com/en/dev/ref/contrib/admin/
This is my dead simple code:
class ArticleAdmin(admin.ModelAdmin):
list_display = ('title', 'category')
Unfortunately, the list_display option is causing the columnar view to appear, but only some of the objects (40 out of 85) are now displaying in the listing. I cannot deduce why certain objects are showing over the others - their fields look like they are filled similarly. It's clearly not paginating, because when I tried it on an admin of another model, it showed only 2 objects out of about 70 objects.
What might be going on here?
[UPDATE] Article Model:
class Article(models.Model):
revision = models.ForeignKey('ArticleRevision', related_name="current_revision")
category = models.ForeignKey('meta.Category')
language = models.ForeignKey('meta.Language', default=get_default_language)
created = models.DateTimeField(auto_now_add=True, editable=False)
changed = models.DateTimeField(auto_now=True, editable=False)
title = models.CharField(max_length=256)
resources = models.ManyToManyField('oer.Resource', blank=True)
image = models.ManyToManyField('media.Image', blank=True)
views = models.IntegerField(editable=False, default=0)
license = models.ForeignKey('license.License', default=get_default_license)
slug = models.SlugField(max_length=256)
difficulty = models.PositiveIntegerField(editable=True, default=0)
published = models.NullBooleanField()
citation = models.CharField(max_length=1024, blank=True, null=True)
Before adding list_display:
After adding list_display:
[UPDATE] This behaviour occurs only when ForeignKey fields are included in list_display tuple. Any of them.
[UPDATE] Category model code:
class Category(models.Model):
title = models.CharField(max_length=256)
parent = models.ForeignKey('self')
project = models.NullBooleanField(default=False)
created = models.DateTimeField(auto_now_add=True, editable=False)
slug = models.SlugField(max_length=256, blank=True)
def __unicode__(self):
return self.title
This behavior is caused by a foreign key relation somewhere that is not declared as nullable, but nonetheless has a null value in the database. When you have a ManyToOne relationship in list_display, the change list class will always execute the query using select_related. (See the get_query_set method in django.contrib.admin.views.ChangeList).
select_related by default follows all foreign keys on each object, so any broken foreign key found by this query will cause data to drop out when the query is evaluated. This is not specific to the admin; you can interactively test it by comparing the results of Article.objects.all() to Article.objects.all().select_related().
There's no simple way to control which foreign keys the admin will look up - select_related takes some parameters, but the admin doesn't expose a way to pass them through. In theory you could write your own ChangeList class and override get_query_set, but I don't recommend that.
The real fix is to make sure your foreign key model fields accurately reflect the state of your database in their null settings. Personally, I'd probably do this by commenting out all FKs on Article other than Category, seeing if that helps, then turning them back on one by one until things start breaking. The problem doesn't have to be with a FK on an article itself; if a revision, language or category has a broken FK that will still cause the join to miss rows. Or if something they relate to has a broken FK, etc etc.