I have the following model:
class Locale (models.Model):
"""
Locale model
"""
locale_id = models.AutoField(primary_key=True)
locale_name = models.CharField(max_length=800)
magister = models.ForeignKey(Magister, on_delete=models.CASCADE)
def get_name(self):
return self.locale_name
In the database, there must be exactly one locale-magister pair.
To create each locale item, an administrator has to upload the locales. This is done via a bulk upload:
try:
lcl=Locale(locale_name = data_dict["locale_name"], magister = data_dict["magister "])
# lcl.full_clean()
locales_list.append(lcl)
rows+=1
if rows==INSERTNUMBER:
try:
Locale.objects.bulk_create(locales_list)
locales_uploaded+=rows
except IntegrityError as e:
print("Error: locale bulk_create "+repr(e))
locales_list=[]
rows=0
I tried using lcl.full_clean() in my bulk upload but I get a UNIQUE constraint failed: zones_locale.locale_name error and only about 1/2 of all locales upload successfully.
I also tried using:
def validate_unique(self, exclude=None):
lcl = Locale.objects.filter(locale_id=self.locale_id)
if lcl.filter(magister=self.magister).exists():
raise ValidationError("item already exists")
But the same error occurs.
I also tried using:
class Meta:
unique_together = (("locale_name", "magister"),)
This did not work either.
From what I can tell, the problem is that there exist locales with the same name that belong to different magisters.
How can I allow locales with the same name to be uploaded while also enforcing the uniqueness of any given locale-magister pair?
Related
Maybe I misunderstand the purpose of Django's update_or_create Model method.
Here is my Model:
from django.db import models
import datetime
from vc.models import Cluster
class Vmt(models.Model):
added = models.DateField(default=datetime.date.today, blank=True, null=True)
creation_time = models.TextField(blank=True, null=True)
current_pm_active = models.TextField(blank=True, null=True)
current_pm_total = models.TextField(blank=True, null=True)
... more simple fields ...
cluster = models.ForeignKey(Cluster, null=True)
class Meta:
unique_together = (("cluster", "added"),)
Here is my test:
from django.test import TestCase
from .models import *
from vc.models import Cluster
from django.db import transaction
# Create your tests here.
class VmtModelTests(TestCase):
def test_insert_into_VmtModel(self):
count = Vmt.objects.count()
self.assertEqual(count, 0)
# create a Cluster
c = Cluster.objects.create(name='test-cluster')
Vmt.objects.create(
cluster=c,
creation_time='test creaetion time',
current_pm_active=5,
current_pm_total=5,
... more simple fields ...
)
count = Vmt.objects.count()
self.assertEqual(count, 1)
self.assertEqual('5', c.vmt_set.all()[0].current_pm_active)
# let's test that we cannot add that same record again
try:
with transaction.atomic():
Vmt.objects.create(
cluster=c,
creation_time='test creaetion time',
current_pm_active=5,
current_pm_total=5,
... more simple fields ...
)
self.fail(msg="Should violated integrity constraint!")
except Exception as ex:
template = "An exception of type {0} occurred. Arguments:\n{1!r}"
message = template.format(type(ex).__name__, ex.args)
self.assertEqual("An exception of type IntegrityError occurred.", message[:45])
Vmt.objects.update_or_create(
cluster=c,
creation_time='test creaetion time',
# notice we are updating current_pm_active to 6
current_pm_active=6,
current_pm_total=5,
... more simple fields ...
)
count = Vmt.objects.count()
self.assertEqual(count, 1)
On the last update_or_create call I get this error:
IntegrityError: duplicate key value violates unique constraint "vmt_vmt_cluster_id_added_c2052322_uniq"
DETAIL: Key (cluster_id, added)=(1, 2018-06-18) already exists.
Why didn't wasn't the model updated? Why did Django try to create a new record that violated the unique constraint?
The update_or_create(defaults=None, **kwargs) has basically two parts:
the **kwargs which specify the "filter" criteria to determine if such object is already present; and
the defaults which is a dictionary that contains the fields mapped to values that should be used when we create a new row (in case the filtering fails to find a row), or which values should be updated (in case we find such row).
The problem here is that you make your filters too restrictive: you add several filters, and as a result the database does not find such row. So what happens? The database then aims to create the row with these filter values (and since defaults is missing, no extra values are added). But then it turns out that we create a row, and that the combination of the cluster and added already exists. Hence the database refuses to add this row.
So this line:
Model.objects.update_or_create(field1=val1,
field2=val2,
defaults={
'field3': val3,
'field4': val4
})
Is to semantically approximately equal to:
try:
item = Model.objects.get(field1=val1, field2=val2)
except Model.DoesNotExist:
Model.objects.create(field1=val1, field2=val2, field3=val3, field4=val4)
else:
item = Model.objects.filter(
field1=val1,
field2=val2,
).update(
field3 = val3
field4 = val4
)
(but the original call is typically done in a single query).
You probably thus should write:
Vmt.objects.update_or_create(
cluster=c,
creation_time='test creaetion time',
defaults = {
'current_pm_active': 6,
'current_pm_total': 5,
}
)
(or something similar)
You should separate your field:
Fields that should be searched for
Fields that should be updated
for example:
If I have the model:
class User(models.Model):
username = models.CharField(max_length=200)
nickname = models.CharField(max_length=200)
And I want to search for username = 'Nikolas' and update this instance nickname to 'Nik'(if no User with username 'Nikolas' I need to create it) I should write this code:
User.objects.update_or_create(
username='Nikolas',
defaults={'nickname': 'Nik'},
)
see in https://docs.djangoproject.com/en/3.1/ref/models/querysets/
This is already answered well in the above.
To be more clear the update_or_create() method should have **kwargs as those parameters on which you want to check if that data already exists in DB by filtering.
select some_column from table_name where column1='' and column2='';
Filtering by **kwargs will give you objects. Now if you wish to update any data/column of those filtered objects, you should pass them in defaults param in update_or_create() method.
so lets say you found an object based on a filter now the default param values are expected to be picked and updated.
and if there's no matching object found based on the filter then it goes ahead and creates an entry with filters and the default param passed.
I'm using Django 1.8.4 in my dev machine using Sqlite and I have these models:
class ModelA(Model):
field_a = CharField(verbose_name='a', max_length=20)
field_b = CharField(verbose_name='b', max_length=20)
class Meta:
unique_together = ('field_a', 'field_b',)
class ModelB(Model):
field_c = CharField(verbose_name='c', max_length=20)
field_d = ForeignKey(ModelA, verbose_name='d', null=True, blank=True)
class Meta:
unique_together = ('field_c', 'field_d',)
I've run proper migration and registered them in the Django Admin. So, using the Admin I've done this tests:
I'm able to create ModelA records and Django prohibits me from creating duplicate records - as expected!
I'm not able to create identical ModelB records when field_b is not empty
But, I'm able to create identical ModelB records, when using field_d as empty
My question is: How do I apply unique_together for nullable ForeignKey?
The most recent answer I found for this problem has 5 year... I do think Django have evolved and the issue may not be the same.
Django 2.2 added a new constraints API which makes addressing this case much easier within the database.
You will need two constraints:
The existing tuple constraint; and
The remaining keys minus the nullable key, with a condition
If you have multiple nullable fields, I guess you will need to handle the permutations.
Here's an example with a thruple of fields that must be all unique, where only one NULL is permitted:
from django.db import models
from django.db.models import Q
from django.db.models.constraints import UniqueConstraint
class Badger(models.Model):
required = models.ForeignKey(Required, ...)
optional = models.ForeignKey(Optional, null=True, ...)
key = models.CharField(db_index=True, ...)
class Meta:
constraints = [
UniqueConstraint(fields=['required', 'optional', 'key'],
name='unique_with_optional'),
UniqueConstraint(fields=['required', 'key'],
condition=Q(optional=None),
name='unique_without_optional'),
]
UPDATE: previous version of my answer was functional but had bad design, this one takes in account some of the comments and other answers.
In SQL NULL does not equal NULL. This means if you have two objects where field_d == None and field_c == "somestring" they are not equal, so you can create both.
You can override Model.clean to add your check:
class ModelB(Model):
#...
def validate_unique(self, exclude=None):
if ModelB.objects.exclude(id=self.id).filter(field_c=self.field_c, \
field_d__isnull=True).exists():
raise ValidationError("Duplicate ModelB")
super(ModelB, self).validate_unique(exclude)
If used outside of forms you have to call full_clean or validate_unique.
Take care to handle the race condition though.
#ivan, I don't think that there's a simple way for django to manage this situation. You need to think of all creation and update operations that don't always come from a form. Also, you should think of race conditions...
And because you don't force this logic on DB level, it's possible that there actually will be doubled records and you should check it while querying results.
And about your solution, it can be good for form, but I don't expect that save method can raise ValidationError.
If it's possible then it's better to delegate this logic to DB. In this particular case, you can use two partial indexes. There's a similar question on StackOverflow - Create unique constraint with null columns
So you can create Django migration, that adds two partial indexes to your DB
Example:
# Assume that app name is just `example`
CREATE_TWO_PARTIAL_INDEX = """
CREATE UNIQUE INDEX model_b_2col_uni_idx ON example_model_b (field_c, field_d)
WHERE field_d IS NOT NULL;
CREATE UNIQUE INDEX model_b_1col_uni_idx ON example_model_b (field_c)
WHERE field_d IS NULL;
"""
DROP_TWO_PARTIAL_INDEX = """
DROP INDEX model_b_2col_uni_idx;
DROP INDEX model_b_1col_uni_idx;
"""
class Migration(migrations.Migration):
dependencies = [
('example', 'PREVIOUS MIGRATION NAME'),
]
operations = [
migrations.RunSQL(CREATE_TWO_PARTIAL_INDEX, DROP_TWO_PARTIAL_INDEX)
]
Add a clean method to your model - see below:
def clean(self):
if Variants.objects.filter("""Your filter """).exclude(pk=self.pk).exists():
raise ValidationError("This variation is duplicated.")
I think this is more clear way to do that for Django 1.2+
In forms it will be raised as non_field_error with no 500 error, in other cases, like DRF you have to check this case manual, because it will be 500 error.
But it will always check for unique_together!
class BaseModelExt(models.Model):
is_cleaned = False
def clean(self):
for field_tuple in self._meta.unique_together[:]:
unique_filter = {}
unique_fields = []
null_found = False
for field_name in field_tuple:
field_value = getattr(self, field_name)
if getattr(self, field_name) is None:
unique_filter['%s__isnull' % field_name] = True
null_found = True
else:
unique_filter['%s' % field_name] = field_value
unique_fields.append(field_name)
if null_found:
unique_queryset = self.__class__.objects.filter(**unique_filter)
if self.pk:
unique_queryset = unique_queryset.exclude(pk=self.pk)
if unique_queryset.exists():
msg = self.unique_error_message(self.__class__, tuple(unique_fields))
raise ValidationError(msg)
self.is_cleaned = True
def save(self, *args, **kwargs):
if not self.is_cleaned:
self.clean()
super().save(*args, **kwargs)
One possible workaround not mentioned yet is to create a dummy ModelA object to serve as your NULL value. Then you can rely on the database to enforce the uniqueness constraint.
Thanks for taking time to read my question.
I have a django app with the following model:
class UserProfile(models.Model):
user = models.OneToOneField(User)
...
class Visit(models.Model):
profile = models.ForeignKey(UserProfile)
date = models.DateField(auto_now_add=True, db_index=True)
ip = models.IPAddressField()
class Meta:
unique_together = ('profile', 'date', 'ip')
In a view:
profile = get_object_or_404(Profile, pk = ...)
get, create = Visit.objects.get_or_create(profile=profile, date=now.date(), ip=request.META['REMOTE_ADDR'])
if create: DO SOMETHING
Everything works fine, except that the Postgres Logs are full with duplicate key errors:
2012-02-15 14:13:44 CET ERROR: duplicate key value violates unique constraint "table_visit_profile_id_key"
2012-02-15 14:13:44 CET STATEMENT: INSERT INTO "table_visit" ("profile_id", "date", "ip") VALUES (1111, E'2012-02-15', E'xx.xx.xxx.xxx') RETURNING "table_visit"."id"
Tried different solution e.g.
from django.db import transaction
from django.db import IntegrityError
#transaction.commit_on_success
def my_get_or_create(prof, ip):
try:
object = Visit.objects.create(profile=prof, date=datetime.now().date(), ip=ip)
except IntegrityError:
transaction.commit()
object = Visit.objects.get(profile=prof, date=datetime.now().date(), ip=ip)
return object
....
created = my_get_or_create(prof, request.META['REMOTE_ADDR'])
if created: DO SOMETHING
This only helps for MySQL? Does anyone know how to avaid the duplicate key value errors for postgres?
Another possible reason for these errors in get_or_create() is data type mismatch in one of the search fields - for example passing False instead of None into a nullable field. The .get() inside .get_or_create() will not find it and Django will continue with new row creation - which will fail due to PostgreSQL constraints.
I had issues with get_or_create when using postgres. In the end I abandoned the boilerplate code for traditional:
try:
jobInvite = Invite.objects.get(sender=employer.user, job=job)
except Invite.DoesNotExist:
jobInvite = Invite(sender=employer.user, job=job)
jobInvite.save()
# end try
Have you at some point had unique=True set on Visit's profile field?
It looks like there's been a unique constraint generated for postgres that's still in effect. "table_visit_profile_id_key" is what it's auto generated name would be, and naturally it would cause those errors if you're recording multiple visits for a user.
If this is the case, are you using South to manage your database changes? If you aren't, grab it!
PostgreSQL behaves somewhat differently in some subtle queries, which results in IntegrityError errors, especially after you switch to Django 1.6. Here's the solution - you need to add select_on_save option to each failing model:
class MyModel(models.Model):
...
class Meta:
select_on_save = True
It's documented here: Options.select_on_save
I'm trying to write an internal API in my application without necessarily coupling it with the database.
class Product(models.Model):
name=models.CharField(max_length=4000)
price=models.IntegerField(default=-1)
currency=models.CharField(max_length=3, default='INR')
class Image(models.Model):
# NOTE -- Have changed the table name to products_images
width=models.IntegerField(default=-1)
height=models.IntegerField(default=-1)
url=models.URLField(max_length=1000, verify_exists=False)
product=models.ForeignKey(Product)
def create_product:
p=Product()
i=Image(height=100, widght=100, url='http://something/something')
p.image_set.add(i)
return p
Now, when I call create_product() Django throws up an error:
IntegrityError: products_images.product_id may not be NULL
However, if I call p.save() & i.save() before calling p.image_set.add(i) it works. Is there any way that I can add objects to a related object set without saving both to the DB first?
def create_product():
product_obj = Product.objects.create(name='Foobar')
image_obj = Image.objects.create(height=100, widght=100, url='http://something/something', product=product_obj)
return product_obj
Explanation:
Product object has to be created first and then assign it to the Image object because id and name here is required field.
I am wondering why wouldn't you not require to make a product entry in DB in first case? If there is any specific reason then i may suggest you some work around?
EDIT: Okay! i think i got you, you don't want to assign a product to an image object initially. How about creating a product field as null is equal to true.
product = models.ForeignKey(Product, null=True)
Now, your function becomes something like this:
def create_product():
image_obj = Image.objects.create(height=100, widght=100, url='http://something/something')
return image_obj
Hope it helps you?
I got same issue with #Saurabh Nanda
I am using Django 1.4.2. When I read in django, i see that
# file django/db/models/fields/related.py
def get_query_set(self):
try:
return self.instance._prefetched_objects_cache[rel_field.related_query_name()]
except (AttributeError, KeyError):
db = self._db or router.db_for_read(self.model, instance=self.instance)
return super(RelatedManager,self).get_query_set().using(db).filter(**self.core_filters)
# file django/db/models/query.py
qs = getattr(obj, attname).all()
qs._result_cache = vals
# We don't want the individual qs doing prefetch_related now, since we
# have merged this into the current work.
qs._prefetch_done = True
obj._prefetched_objects_cache[cache_name] = qs
That 's make sese, we only need to set property _prefetched_objects_cache for the object.
p = Product()
image_cached = []
for i in xrange(100):
image=Image(height=100, widght=100, url='http://something/something')
image_cached.append(image)
qs = p.images.all()
qs._result_cache = image_cached
qs._prefetch_done = True
p._prefetched_objects_cache = {'images': qs}
Your problem is that the id isn't set by django, but by the database (it's represented in the database by an auto-incremented field), so until it's saved there's no id. More about this in the documentation.
I can think of three possible solutions:
Set a different field of your Image model as the primary key (documented here).
Set a different field of your Production model as the foreign key (documented here).
Use django's database transactions API (documented here).
i have i little problem, and that is how can serialize a django query with defer ?
I have this model :
class Evento(models.Model):
nome=models.CharField(max_length=100)
descricao=models.CharField(max_length=200,null=True)
data_inicio= models.DateTimeField()
data_fim= models.DateTimeField()
preco=models.DecimalField(max_digits=6,decimal_places=2)
consumiveis= models.CharField(max_length=5)
dress_code= models.CharField(max_length=6)
guest_list=models.CharField(max_length=15)
local = models.ForeignKey(Local)
user= models.ManyToManyField(User,null=True,blank=True)
def __unicode__(self):
return unicode('%s %s'%(self.nome,self.descricao))
my query is this :
eventos_totais = Evento.objects.defer("user").filter(data_inicio__gte=default_inicio,
data_fim__lte=default_fim)
it works fine i think (how can i check if the query has realy defer the field user ? ) but when i do:
json_serializer = serializers.get_serializer("json")()
eventos_totais = json_serializer.serialize(eventos_totais,
ensure_ascii=False,
use_natural_keys=True)
it always folow the natural keys for user and local, i need natural keys for this query because of the fields local. But i do not need the field user.
To serialize a subset of your models fields, you need to specify the fields argument to the serializers.serialize()
from django.core import serializers
data = serializers.serialize('xml', SomeModel.objects.all(), fields=('name','size'))
Ref: Django Docs