models.py
class Contact(models.Model):
attributes = GenericRelation(
AttributeValue,related_query_name='contact',content_type_field='target_content_type',object_id_field='target_object_id')
class AttributeValue(models.Model):
attribute = models.ForeignKey(Attribute, related_name="attribute")
# the object instance we are associating this attribute to
target_content_type = models.ForeignKey(ContentType, related_name="attribute_value_target_content_type",
on_delete=models.CASCADE, blank=True, null=True)
target_object_id = models.PositiveIntegerField(blank=True, null=True, db_index=True)
target = GenericForeignKey('target_content_type', 'target_object_id')
class Attribute(models.Model):
name = CHarFIeld()
I want to get all the contacts that follow both the conditions below
Have an AttributeValue model object in attributes field with
attributes__attribute__name = 'crop_name' and
attributes__value='groundnut'
Have an AttributeValue model object in attributes field with attributes__attribute__name = 'crop_season' and attributes__value='winter'
One way to achieve this is mentioned as follows:
Contact.objects.all().filter(Q(attributes__attribute__name='crop_name') & Q(attributes__value='groundnut')).filter(Q(attributes__attribute__name='crop_season') & Q(attributes__value='winter'))
The above mentioned query works fine. But I want to construct a single such query that can be given into .filter()
i.e. something like
Contact.objects.filter(query)
I tried doing something like
Contact.objects.filter(Q(Q(attributes__attribute__name='crop_name') & Q(attributes__value='groundnut'))& Q(Q(attributes__attribute__name='crop_season') & Q(attributes__value='winter')))
Expecting that query would respect the braces, but it doesn't like that i guess
P.S. I am using django(1.11.4) + postgres(9.5.7) combination
Related
I have a model in Django/PostgreSQL project and want to add following constraints to three nullable fields: either all fields are NULL, either all of them aren't.
Here's code (simplified):
class SomeModel(models.Model):
...
a = models.IntegerField(nullable=True)
b = models.DateTimeField(nullable=True)
c = models.DateTimeField(nullable=True)
...
class Meta:
constraints = [
models.CheckConstraint(
check=(
(Q(a__isnull=True) & Q(b__isnull=True) & Q(c__isnull=True)) |
(Q(a__isnull=False) & Q(b__isnull=False) & Q(c__isnull=False))
)
)
]
If I understand correctly, I've just described two possible states of those three fields. First is "all three are NULL", second is "none of them are NULL".
But what I got, actually, is "none of them can be NULL". Django admin panel insists on filling all of the fields, they all are mandatory. How can I fix this behaviour? Thanks!
This is not due to the constraints, you should specify blank=True [Django-doc] when you want to allow to leave form fields blank, and thus default to None/NULL:
class SomeModel(models.Model):
# …
a = models.IntegerField(null=True, blank=True)
b = models.DateTimeField(null=True, blank=True)
c = models.DateTimeField(null=True, blank=True)
class Meta:
constraints = [
models.CheckConstraint(
check=Q(a=None, b=None, c=None) |
Q(a__isnull=False, b__isnull=False, c__isnull=False),
name='all_or_none_null'
)
]
I've read the docs and searched this site but cannot seem to find a solution to sorting field values by the order in which they are declared. The docs state that adding ordered = True to the class Meta will solve this problem -
class MySchema(Schema):
class Meta:
ordered = True
However, I am not using class Meta in my schema. My schema simply looks like -
class MySchema(Schema):
id = fields.Integer()
name = fields.Str()
category = fields.Str()
So in this situation, how and where would I set ordered = True? Thanks!
I solved the issue by changing my schema class to -
class MySchema(Schema):
class Meta:
ordered = True
id = fields.Integer()
name = fields.Str()
category = fields.Str()
and then also adding JSON_SORT_KEYS=False to my app's config.py file.
I have tried to think about how the following SQL query would be structured as a Django ORM query but I have had no luck in my multiple attempts. Can anyone help?
SELECT targets_genetarget.gene, count(targets_targetprediction.gene) as total
FROM targets_genetarget
LEFT OUTER JOIN targets_targetprediction on targets_targetprediction.gene =
targets_genetarget.gene
WHERE list_name LIKE %s
GROUP BY targets_genetarget.gene
class GeneTarget(models.Model):
list_name = models.CharField(max_length=100)
gene = models.CharField(max_length=50)
date_added = models.DateField(auto_now=True)
class Meta:
unique_together = (('list_name', 'gene'),)
def __str__(self):
return self.list_name
class TargetPrediction(models.Model):
specimen_id = models.CharField(max_length=100)
patient_peptide = models.ForeignKey(Peptide, on_delete=models.CASCADE, verbose_name="Peptide", related_name="predictions")
allele = models.ForeignKey(Allele, on_delete=models.CASCADE, verbose_name="Allele", related_name="predictions")
gene = models.CharField(max_length=50)
class Meta:
unique_together = (('specimen_id', 'patient_peptide', 'allele', 'gene'),)
def get_absolute_url(self):
return f'/samples/specid-{self.specimen_id}'
def __str__(self):
return (f'Specimen: {self.specimen_id} Peptide: {self.patient_peptide} Allele: {self.allele} Gene: {self.gene} ')
There's nothing stopping you declaring the TargetPrediction.gene field as a foreign key using the to_field attribute, so you wouldn't need to change the data at all:
class TargetPrediction(models.Model):
...
gene = models.ForeignKey("GeneTarget", to_field="gene")
Now your query simply becomes:
GeneTarget.objects.filter(list_name="whatever").values("gene").annotate(total=Count("targetprediction"))
I'm having a problem creating (nested) serializers for the following models:
class Chapter(Model):
uuid = UUIDField(primary_key=True, editable=False)
description = TextField(blank=True)
class Section(Model):
uuid = UUIDField(primary_key=True, editable=False)
description = TextField(blank=True)
chapter = ForeignKey(Chapter, related_name='sections', on_delete=CASCADE)
Here is the serializer for the Chapter model with the create method:
class ChapterSerializer(ModelSerializer):
uuid = UUIDField(read_only=False)
sections = SectionSerializer(many=True, read_only=False)
class Meta:
model = Chapter
fields = ('uuid', 'description', 'sections')
def create(self, validated_data):
sections = validated_data.pop('sections', [])
chapter = Chapter.objects.create(**validated_data)
for section in sections:
section.update({'chapter': chapter})
section = Section.objects.create(**section)
return chapter
And here are two slightly different variants of the Section serializer:
class SectionSerializer(ModelSerializer):
uuid = UUIDField(read_only=False)
chapter = PrimaryKeyRelatedField(read_only=true)
class Meta:
model = Section
fields = ('uuid', 'description', 'chapter')
class SectionSerializer(ModelSerializer):
uuid = UUIDField(read_only=False)
chapter = PrimaryKeyRelatedField(queryset=Chapter.objects.all())
class Meta:
model = Section
fields = ('uuid', 'description', 'chapter')
Now if I try to create a new Chapter with nested Sections and the PrimaryKeyRelatedField in the Section serializer has the queryset parameter set, I get the following error:
'sections': [{'chapter': ['Invalid pk "x" - object does not exist.']}]
If I use the variant with the read_only=true parameter, creating a new Chapter with nested Sections works, but now I can no longer create a new Section (Chapter field is set to an existing Chapter UUID) because the chapter field is removed while validating the input data.
django.db.utils.IntegrityError: null value in column "chapter_id" violates not-null constraint
I think I could solve this by duplicating the SectionSerializer, but this seems to be a very crude solution ...
Anyone knowing of an better approach?
OK, answering my own question:
I finally found a way to get a "nestable" and a "writeable" version of the SectionSerializer without code duplication:
class NestedSectionSerializer(ModelSerializer):
uuid = UUIDField(read_only=False)
class Meta:
model = Section
exclude = ('chapter', )
class SectionSerializer(NestedSectionSerializer):
url = serializers.HyperlinkedIdentityField(view_name='section-detail')
class Meta:
model = Section
fields = '__all__'
class ChapterSerializer(ModelSerializer):
url = serializers.HyperlinkedIdentityField(view_name='chapter-detail')
uuid = UUIDField(read_only=False)
sections = NestedSectionSerializer(many=True, read_only=False)
class Meta:
model = Chapter
fields = '__all__'
def create(self, validated_data):
sections = validated_data.pop('sections', [])
chapter = Chapter.objects.create(**validated_data)
for section in sections:
section.update({'chapter': chapter})
section = Section.objects.create(**section)
return chapter
The key here ist to explicitly exclude the reverence to chapter in the "nested" serializer but add it again in the "writeable" serializer. This even scales to deeply nested structures!
And by using inheritance I can avoid most code duplication.
I just pulled my hair about this very same question.
The answer is actually in the DRF documentation: you need to explicitely define the queryset argument for the PrimaryKeyRelatedField if you want them to be writable.
In your case, only the second variant of SectionSerializer is necessary.
I know that this inconvenient is very presented, may be that I need learn more about of serializer relationships
I have the following model:
class Field(models.Model):
FIELD_TYPE_NATURE = 'Grama natural'
FIELD_TYPE_ARTIFICIAL = 'Grama sintetica'
FIELD_TYPE_CHOICES = (
(FIELD_TYPE_NATURE, u'Grama natural'),
(FIELD_TYPE_ARTIFICIAL, u'Grama sintetica'),
)
MODALITY_11 = 'Fútbol 11'
MODALITY_8 = 'Fútbol 8'
MODALITY_CHOICES = (
(MODALITY_11, u'Fútbol 11'),
(MODALITY_8, u'Fútbol 8'),
)
name = models.CharField(
max_length=150,
unique=True,
db_index=True,
primary_key=True,
)
field_type = models.CharField(
choices=FIELD_TYPE_CHOICES,
default=False,
blank=False,
max_length=20,
verbose_name=('Tipo de material/grama de la cancha')
)
modality = models.CharField(
max_length=40,
blank=False,
verbose_name='Modalidad'
)
photo = models.ImageField(upload_to='fields', blank=True, null=True)
location = models.CharField(max_length=150, blank=False)
def __str__(self):
return '%s %s %s' % (self.name, self.field_type, self.location)
My serializer is the following:
class FieldSerializer(serializers.HyperlinkedModelSerializer):
#url = serializers.HyperlinkedIdentityField(view_name='field-detail',)
class Meta:
model = Field
fields = ('url', 'name','field_type','modality','photo','location')
My viewset is:
class FieldViewSet(viewsets.ModelViewSet):
queryset = Field.objects.all()
serializer_class = FieldSerializer
This is my router:
router = routers.DefaultRouter()
router.register(r'fields', FieldViewSet)
And my url:
...
url(r'^api/', include(router.urls)),
...
When I go to the http://localhost:8000/api/fields/ url I get the following message:
File "/home/bgarcial/.virtualenvs/fuupbol2/lib/python3.5/site-packages/rest_framework/relations.py", line 386, in to_representation
raise ImproperlyConfigured(msg % self.view_name)
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for **hyperlinked relationship using view name "field-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.**
[11/Nov/2016 16:39:53] "GET /api/fields/ HTTP/1.1" 500 187477
When I use HyperlinkedIdentityField in my FieldSerializer class:
class FieldSerializer(serializers.HyperlinkedModelSerializer):
url = serializers.HyperlinkedIdentityField(view_name='field-detail',)
class Meta:
model = Field
fields = ('url', 'name','field_type','modality','photo','location')
I follow getting the same error.
Althought when I go to the url http://localhost:8000/api/fields/ I want get is a list of my objects, then is possible that I should put:
url = serializers.HyperlinkedIdentityField(view_name='field-list',)
?
I use HyperlinkedIdentityField according to:
This field can be applied as an identity relationship, such as the
'url' field on a HyperlinkedModelSerializer. It can also be used for
an attribute on the object.
I put the field-list in my view_name attribute and I get the error related
Could not resolve URL for hyperlinked relationship using view name "field-list". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
I don't understand the situations when I should use view_name attribute in relation to if I wnt get a list objects, a object detail and so ... although here explain something about it.
When I should use HyperlinkedModelSerializer and ModelSerializer