Develop Reference

Solution to filter by Cumulative sum and error: Window is disallowed in the filter clause

This is follow-up to a question to:
Filter Queries which sum of their amount field are greater or lesser than a number
which is supposed to be solved. Answer suggests using Window function with filter but this results in a error:
django.db.utils.NotSupportedError: Window is disallowed in the filter clause.
Comment from #atabak hooshangi suggests removing the Window function, but query doesn't work in intended way after that. Any ideas to solve this problem?

let's say we have these 2 models:
class Developer(models.Model):
first_name = models.CharField(max_length=40, null=False, blank=False,
unique=True)
last_name = models.CharField(max_length=40, null=False, blank=False,
unique=True)
profession = models.CharField(max_length=100, null=False)
cv = models.FileField(upload_to=upload_cv_location, null=True, blank=True)
description = models.TextField()
img = models.ImageField(upload_to=upload_location, null=True, blank=True)
class Meta:
verbose_name = 'Developer'
verbose_name_plural = 'Developers'
ordering = ('first_name',)
def __str__(self):
return f'{self.first_name} {self.last_name}'
class Skill(models.Model):
developer = models.ForeignKey(to=Developer, on_delete=models.CASCADE)
category = models.ForeignKey(to=SkillCategory, on_delete=models.SET_NULL,
null=True)
name = models.CharField(max_length=50, null=False)
priority = models.PositiveIntegerField()
class Meta:
ordering = ('-priority',)
def __str__(self):
return f'{self.name} skill of {self.developer}'
As you can see , we have a developer model which has relationship with skill. Each developer can have multiple skills.
now consider we want to get the developers whos sum of their priorities are greater than a number.
The orm query should work this way :
from django.db.models import Sum
developers = Developer.objects.annotate(tot=Sum('skill__priority')).filter(tot__gt=250).all()
The output will be the developers who has greater than 250 priority_sum .
You can filter tot which is an annotated variable in any way you want.
like .filter(tot__lte)
or
.filter(tot__lt)
I hope this is what you were looking for.

How to create a django queryset object for inner join?

I have two tables.
class DibbsSpiderDibbsMatchedProductFieldsDuplicate(models.Model):
nsn = models.TextField()
nsn2 = models.TextField()
cage = models.TextField()
part_number = models.TextField()
company_name = models.TextField(blank=True, null=True)
supplier = models.TextField(db_column='Supplier', blank=True, null=True) # Field name made lowercase.
cost = models.CharField(db_column='Cost', max_length=15, blank=True, null=True) # Field name made lowercase.
list_price = models.CharField(db_column='List_Price', max_length=15, blank=True, null=True) # Field name made lowercase.
gsa_price = models.CharField(db_column='GSA_Price', max_length=15, blank=True, null=True) # Field name made lowercase.
hash = models.TextField()
nomenclature = models.TextField()
technical_documents = models.TextField()
solicitation = models.CharField(max_length=32)
status = models.CharField(max_length=16)
purchase_request = models.TextField()
issued = models.DateField()
return_by = models.DateField()
file = models.TextField()
vendor_part_number = models.TextField()
manufacturer_name = models.TextField(blank=True, null=True)
product_name = models.TextField(blank=True, null=True)
unit = models.CharField(max_length=15, blank=True, null=True)
class Meta:
managed = False
db_table = 'dibbs_spider_dibbs_matched_product_fields_duplicate'
class DibbsSpiderSolicitation(models.Model):
line_items = models.IntegerField()
nsn = models.TextField()
nomenclature = models.TextField()
technical_documents = models.TextField()
purchase_request = models.TextField()
class Meta:
managed = False
db_table = 'dibbs_spider_solicitation'
What will be the equivalent django query for the inner join of two tables on the column nsn?
My views function will be like
def inner(request,nsn):
u_m = DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.filter(nsn2__icontains=id)
c_m = DibbsSpiderSolicitation.objects.filter(nsn__icontains=id)
obj = .......................
context = {'obj':obj}
return render(request,,"a.html",context)
the queryset should return the combination of two tables according to the common nsn.
the obj should return the combination of u_m and c_m. If u_m contains only one rows and c_m contains many rows then the obj must replicate the values of u_m.

You can try some of the options:
Adding foreign key constraint and use select_related as per this post
Raw query as mentioned in this stackoverflow post and another post with custom joins
3. Using IN query as per the following logic:
DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.filter(
nsn2__in=DibbsSpiderSolicitation.objects.filter(nsn__icontains='text_to_search').values('origin'))

First, great model names. Let's alias them:
DibbsSpiderDibbsMatchedProductFieldsDuplicate is Apples; DibbsSpiderSolicitation is Oranges
inner_qs = Apples.objects.all().extra(
tables=("yourapp_oranges",),
where=("yourapp_apples.nsn=yourapp_oranges.nsn",),
)
The documentation mentions that this api will be deprecated:
https://docs.djangoproject.com/en/4.0/ref/models/querysets/#extra

Option #1 - Introduce a ForeignKey (Recommended):
Under the class DibbsSpiderDibbsMatchedProductFieldsDuplicate add:
fkey = models.ForeignKey('DibbsSpiderSolicitation')
then you can easily access their join:
obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.Objects.filter(fkey__nsn).select_related()
Now it is your choice what you wish to do with nsn2
Option #2 - without a ForeigKey:
Raw SQL:
obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.extra(where = ['''SELECT *
FROM DibbsSpiderSolicitation
INNER JOIN DibbsSpiderDibbsMatchedProductFieldsDuplicate
ON DibbsSpiderSolicitation.nsn = DibbsSpiderDibbsMatchedProductFieldsDuplicate.nsn2;'''])
# or
obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.raw('''SELECT *
FROM DibbsSpiderSolicitation
INNER JOIN DibbsSpiderDibbsMatchedProductFieldsDuplicate
ON DibbsSpiderSolicitation.nsn = DibbsSpiderDibbsMatchedProductFieldsDuplicate.nsn2;''')
Using filter:
obj = DibbsSpiderSolicitation.objects.filter(nsn__in=DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.nsn2)
Sorry, I was not able to test any.

How do I call a specific field in a model into another model?

I am new to django. I wanted to know if it was possible to call a specific field in a model into another model.
The goal is to update a the quantity of a specific product in the database and generate a receipt for it.
Here's the example:
models.py:
class Product(models.Model):
name = models.CharField(max_length=300, null=True)
price = models.FloatField(null=True)
quantity = models.IntegerField(default='0', blank=True, null=True)
class UpdateStock(models.Model):
date = models.DateTimeField(default=timezone.now)
wayBill_Number = models.CharField(max_length=300, null=True)
product_Name = models.ForeignKey(Product.name, null=True, on_delete= models.SET_NULL)
quantity = models.ForeignKey(Product.quantity, null=True, on_delete= models.SET_NULL)
I just want to select the product and the quantity to update in the database but I am unable to do so.

A ForeignKey is supposed to refer to another model, not to one of its fields.
So the first thing you have to do it to edit your UpdateStock model this way :
class UpdateStock(models.Model):
date = models.DateTimeField(default=timezone.now)
wayBill_Number = models.CharField(max_length=300, null=True)
product = models.ForeignKey('Product', null=True, on_delete=models.SET_NULL) # Here
quantity = models.IntegerField(default='0', blank=True, null=True) # Here
So you can bound your product to your stock_update when you create it:
stock_update = UpdateStock.objects.create(..., product=your_product_obj, ...)
And you will then be able to access any product's field from this stock_update:
product = stock_update.product
print(product.quantity)
product.quantity = product.quantity + stock_update.quantity
print(product.quantity)
product.save()
But I strongly advise you to read more about many-to-one relationships in the docs.

Django multiple foreign key to a same table

I need to log the transaction of the item movement in a warehouse. I've 3 tables as shown in the below image. However Django response error:
ERRORS:
chemstore.ItemTransaction: (models.E007) Field 'outbin' has column name 'bin_code_id' that is used by another field.
which is complaining of multiple uses of the same foreign key. Is my table design problem? or is it not allowed under Django? How can I achieve this under Django? thankyou
DB design
[Models]
class BinLocation(models.Model):
bin_code = models.CharField(max_length=10, unique=True)
desc = models.CharField(max_length=50)
def __str__(self):
return f"{self.bin_code}"
class Meta:
indexes = [models.Index(fields=['bin_code'])]
class ItemMaster(models.Model):
item_code = models.CharField(max_length=20, unique=True)
desc = models.CharField(max_length=50)
long_desc = models.CharField(max_length=150, blank=True)
helper_qty = models.DecimalField(max_digits=10, decimal_places=4)
unit = models.CharField(max_length=10, blank=False)
def __str__(self):
return f"{self.item_code}"
class Meta:
verbose_name = "Item"
verbose_name_plural = "Items"
indexes = [models.Index(fields=['item_code'])]
class ItemTransaction(models.Model):
trace_code = models.CharField(max_length=20, unique=False)
item_code = models.ForeignKey(
ItemMaster, related_name='trans', on_delete=models.CASCADE, null=False)
datetime = models.DateTimeField(auto_now=False, auto_now_add=False)
qty = models.DecimalField(max_digits=10, decimal_places=4)
unit = models.CharField(max_length=10, blank=False)
action = models.CharField(
max_length=1, choices=ACTION, blank=False, null=False)
in_bin = models.ForeignKey(
BinLocation, related_name='in_logs', db_column='bin_code_id', on_delete=models.CASCADE, null=False)
out_bin = models.ForeignKey(
BinLocation, related_name='out_logs', db_column='bin_code_id', on_delete=models.CASCADE, null=False)
remarks = models.TextField(blank=True)
def __str__(self):
return f"{self.trace_code} {self.datetime} {self.item_code} {dict(ACTION)[self.action]} {self.qty} {self.unit} {self.in_bin} {self.out_bin}"

you have same db_column in two fields so change it
in_bin = models.ForeignKey(
BinLocation, related_name='in_logs', db_column='bin_code_id', on_delete=models.CASCADE, null=False)
out_bin = models.ForeignKey(
BinLocation, related_name='out_logs', db_column='other_bin_code', on_delete=models.CASCADE, null=False) /*change db_column whatever you want but it should be unique*/

If are linked to the same model name, You should use different related_name for each foreign_key filed . here is the exemple :
address1 = models.ForeignKey(Address, verbose_name=_("Address1"),related_name="Address1", null=True, blank=True,on_delete=models.SET_NULL)
address2 = models.ForeignKey(Address, verbose_name=_("Address2"),related_name="Address2", null=True, blank=True,on_delete=models.SET_NULL)

thank you for everyone helped. According to Aleksei and Tabaane, it is my DB design issue (broken the RDBMS rule) rather than Django issue. I searched online and find something similar: ONE-TO-MANY DB design pattern
In my case, I should store in bin and out bin as separated transaction instead of both in and out in a single transaction. This is my solution. thankyou.
p.s. alternative solution: I keep in bin and out bin as single transaction, but I don't use foreign key for bins, query both in bin and out bin for the bin selection by client application.

Merge two/objects querysets with Django

I have the following piece of code. I'm using it to return json so Datatables can render it. I pass in query parameters.
def map_query(type_, type_model, type_pk, query_data, request):
type_results_query = None
problem_data = get_model_query_data(query_data, Problem)
problems_filtered = Problem.objects.filter(**problem_data)
if request.POST:
model_query_data = get_model_query_data(query_data, type_model)
type_results_query = Chgbk.objects.filter(**model_query_data)
print(type_results_query)
return type_results_query
So type_results_query returns data I want. But Problem model has a foreign key on it which links to key on table. I want to get the data from the Problem table into the Chgbk query as well, sort of the two objects merged but I cannot figure out how to do this and it is driving me crazy.
Models would be:
class Chgbk(VNCModel):
chgbk_id = models.IntegerField(primary_key=True)
facility = models.ForeignKey('Facility', models.DO_NOTHING)
create_dt = models.DateTimeField(blank=True, null=True)
mod_dt = models.DateTimeField(blank=True, null=True)
carrier_scac = models.CharField(max_length=25, blank=True, null=True)
carrier_name = models.CharField(max_length=25, blank=True, null=True)
class Problem(VNCModel):
problem_id = models.IntegerField(primary_key=True)
chgbk = models.ForeignKey(Chgbk, models.DO_NOTHING, blank=True, null=True)