Related
I am working on a project named "Super Market Inventory Management System". There are some models requiring many-to-many relation among them.
I tried to add ManyToManyField(to=model, on_delete=models.CASCADE). However, it works but I need to add some extra fields to the bridge table between the two tables.
How can I do It?
Given below is my models.py
class Purchase(models.Model):
pay_status = models.CharField(max_length=50, choices=PAYSTATUS_CHOICES, default="Pending")
date_of_purchase = models.DateTimeField(auto_now_add=True)
last_payment = models.DateTimeField(auto_now=True)
class Product(models.Model):
name = models.CharField(max_length=200)
barcode = models.IntegerField(blank=True, null=True)
description = models.TextField(blank=True, null=True)
# image =
weight = models.TextField(blank=True, null=True)
status = models.BooleanField(default=True)
price = models.FloatField()
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
class PurchaseProduct(models.Model):
purchase_id = models.ForeignKey(to=Purchase, on_delete=models.CASCADE)
product_id = models.ForeignKey(to=Product, on_delete=models.CASCADE)
unit_price = models.FloatField()
quantity = models.IntegerField()
price = models.FloatField()
In the bridge table I also want to add the unit price and the quantity how can I do?
OR
Is there any alternate way of doing???
However if I do not add unit price and quantity I don't need to create this bridge table all the endings will be done by Django itself but I must require the above mentioned fields in my model
I want to create a sales campaign which stores a list of books (Items). But the book should only be applied to one sales campaign — ie. it should not be able to appear in two campaigns.
I have the following model:
class Campaign(models.Model):
campaign_name = models.CharField(max_length=50, null=False, blank=False, default='Special Offer')
included_items = models.ManyToManyField(Item, blank=True)
active = models.BooleanField(default=True)
fixed_price = models.DecimalField(max_digits=6, blank=True, null=True, decimal_places=2)
But I think the included_items field might be of the wrong field type. From reading other questions and the Django manual, I think I may be approaching this back to front. Perhaps I should be tackling this from the Item model instead? (Shown below for reference)
class Item(models.Model):
sku = models.CharField(
max_length=10, null=True, blank=True,
default=create_new_sku)
title = models.CharField(max_length=254)
genre = models.ManyToManyField('Genre', blank=True)
author = models.ManyToManyField('Author', blank=True)
description = models.TextField()
age_range = models.ManyToManyField(
'Age_range')
image_url = models.URLField(max_length=1024, null=True, blank=True)
image = models.ImageField(null=True, blank=True)
price = models.DecimalField(max_digits=6, decimal_places=2, default=0.00)
discount = models.DecimalField(max_digits=2, decimal_places=0, default=0)
set_sale_price = models.DecimalField(max_digits=6, decimal_places=2, default=0.00)
original_sale_price = models.DecimalField(max_digits=6, decimal_places=2, null=True, blank=True)
final_price = models.DecimalField(max_digits=6, decimal_places=2, null=True, blank=False, editable=False)
If each item can only belong to one campaign you should be using a ForeignKey to campaign in the Item model to create your many-to-one relationship
Actually your design is fine.
Using a ForeignKey from #Henty's answer on the Item model still runs into issues where if a campaign becomes inactive (active=False), the Item model needs to nullify the ForeignKey to allow other campaigns to offer it. In addition, an Item model's data should only have information about that instance. To me I think it's weird having a foreign key to a campaign in an Item model since that data is irrelevant to a book. You probably want to read up on data normalization.
That being said, you should manually specify your many-to-many intermediary table as you'll need to apply a unique constraint in it so that only one active campaign can offer the book.
This intermediary table will also have fields such as the discount or sale_price of the book since different campaigns can offer different discounts/prices. I'm assuming price in your Item model is the base retail price on your book so discount, set_sale_price, original_sale_price, and final_price are not needed - again, refer back to data normalization.
In addition, you will need to copy over the active field from your Campaign instance to your intermediary table because it will be needed for the unique constraint. This is done by overriding the save method on your intermediary table to copy over the active value from the Campaign instance.
You'll also have to override the save method on your Campaign model to update the active field on your intermediary instances when you activate/deactivate a campaign.
class Campaign(models.Model):
campaign_name = ...
included_items = models.ManyToManyField(
Item,
through='CampaignItem',
through_fields=('campaign', 'item')
)
active = ...
fixed_price = ...
def save(self, *args, **kwargs):
# pre-save, update associated campaign-item instances
CampaignItem.objects.filter(campaign=self).update(active=self.active)
super().save(*args, **kwargs)
class CampaignItem(models.Model):
campaign = models.ForeignKey(Campaign, on_delete=models.CASCADE)
item = models.ForeignKey(Item, on_delete=models.CASCADE)
active = models.BooleanField(editable=False)
discount = ...
sale_price = ...
# add any other relevant fields related to this campaign item
class Meta:
# add constraint where item can only be in one active campaign
constraints = [
UniqueConstraint(fields=['item'],
condition=Q(active=True),
name='unique_active_item')
]
def save(self, *args, **kwargs):
# copy over the `active` value from campaign
self.active = self.campaign.active
super().save(*args, **kwargs)
What is the deal: I'm crating a site where different types of objects will be evaluated, like restaurants, beautysalons, car services (and much more).
At the beginning I start with one app with with Polymorfic Model:
models.py:
from django.db import models
from users.models import ProfileUser
from django.utils import timezone
from polymorphic.models import PolymorphicModel
class Object(PolymorphicModel):
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
title = models.CharField(max_length=300)
city = models.ForeignKey(City, on_delete=models.CASCADE)
address = models.CharField(max_length=300)
phone = models.CharField(max_length=20, default='')
email = models.CharField(max_length=100, default='')
site = models.CharField(max_length=100, default='')
facebook = models.CharField(max_length=100, default='')
instagram = models.CharField(max_length=100, default='')
content = models.TextField()
rating = models.DecimalField(default=10.0, max_digits=5, decimal_places=2)
created_date = models.DateTimeField(default=timezone.now)
approved_object = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
def __str__(self):
return f"{self.title}"
class Restaurant(Object):
seats = models.IntegerField()
bulgarian_kitchen = models.BooleanField(default=False)
italian_kitchen = models.BooleanField(default=False)
french_kitchen = models.BooleanField(default=False)
sea_food = models.BooleanField(default=False)
is_cash = models.BooleanField(default=False)
is_bank_card = models.BooleanField(default=False)
is_wi_fi = models.BooleanField(default=False)
category_en_name = models.CharField(max_length=100, default='restaurants')
category_bg_name = models.CharField(max_length=100, default='Ресторанти')
bg_name = models.CharField(max_length=100, default='Ресторант')
is_garden = models.BooleanField(default=False)
is_playground = models.BooleanField(default=False)
class SportFitness(Object):
is_fitness_trainer = models.BooleanField(default=False)
category_en_name = models.CharField(max_length=100, default='sportfitness')
category_bg_name = models.CharField(max_length=100, default='Спорт и фитнес')
bg_name = models.CharField(max_length=100, default='Спорт и фитнес')
class CarService(Object):
is_parts_clients = models.BooleanField(default=False)
category_en_name = models.CharField(max_length=100, default='carservice')
category_bg_name = models.CharField(max_length=100, default='Автосервизи')
bg_name = models.CharField(max_length=100, default='Автосервиз')
class Comment(models.Model):
object = models.ForeignKey(Object, on_delete=models.CASCADE, related_name='comments')
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
content = models.TextField()
rating = models.TextField()
approved_object = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
created_date = models.DateTimeField(default=timezone.now)
def __str__(self):
return f"{self.content}"
class Images(models.Model):
object = models.ForeignKey(Object, default=None, on_delete=models.CASCADE)
image = models.ImageField(upload_to='attachments',
verbose_name='Image')
class ObjectCoordinates(models.Model):
object = models.ForeignKey(Object, on_delete=models.CASCADE, related_name='coordinates')
latitude = models.CharField(max_length=60)
longitude = models.CharField(max_length=60)
Don't mention that name Object is wrong, I already know that :)
So all logic about different objects was in one App and this start to cause some problems, like:
views.py:
def show_object(request, category, pk, page_num):
categories = {'restaurants' : 'Restaurant', 'sportfitness' : 'SportFitness', 'carservice' : 'CarService'} # probably this is not good way to do it
obj = apps.get_model('objects', categories[category]).objects.get(id=pk)
def show_all_objects(request, category, page_num, city=None):
params_map = {
'restaurants': Restaurant,
'sportfitness': SportFitness,
'carservice': CarService,
}
objects = Object.objects.instance_of(params_map.get(category))
and other problems in templates (a lot of if-else blocks) etc.
So I decide to change whole structure and put every model in different app, so now I have app:restaurants, app:sportfitness, app:carservices, etc. But it begin to cause some problems, again, like this model:
class ObjectCoordinates(models.Model):
object = models.ForeignKey(Object, on_delete=models.CASCADE, related_name='coordinates')
latitude = models.CharField(max_length=60)
longitude = models.CharField(max_length=60)
All of objects (restaurants, car services) has coordinates of map, so I'm not sure how to handle it, with Model ObjectCoordinates . If I create ObjectCoordinates for each of them, respectively a table in BD (then I will have some tables with different names but same structure, which is not very good, because except ObjectCoordinates, models share and other common models like Images and others, so at the end I will have a lot of tables with different names and same structure). Probably I should add one more column for object category, if I got two rows with same id of objects?
Probably change ObjectCoordinates and other common models to ManyToMany relation will prevent identical tables, but I'm not quite sure about that. Other problem is that there is a lot of repeated code (in views, templates). Also, now, I don't know how to get all objects (restaurants, car services) when they do not have common point, like Object model in first scenario with Polymorphic Model. Or I should keep different apps but to create common Model for all objects, and all of them to to inherit it.
Questions:
What structure is better, first one or second one?
What is the best wayt to implement such site (model structure)?
Should I create common point (model) for all models who they will inherit?
Here is my third attempt (notice that Object is renamed to Venue):
from django.db import models
from users.models import ProfileUser
from django.utils import timezone
from polymorphic.models import PolymorphicModel
# Create your models here.
class City(models.Model):
name = models.CharField(max_length=20)
def __str__(self):
return f"{self.name}"
class Category(models.Model):
name = models.CharField(max_length=20)
bg_name = models.CharField(max_length=20, default=None)
category_bg_name = models.CharField(max_length=100, default=None)
def __str__(self):
return f"{self.name}"
class Venue(models.Model):
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
title = models.CharField(max_length=300)
city = models.ForeignKey(City, on_delete=models.CASCADE)
address = models.CharField(max_length=300)
phone = models.CharField(max_length=20, default='')
email = models.CharField(max_length=100, default='')
site = models.CharField(max_length=100, default='')
facebook = models.CharField(max_length=100, default='')
instagram = models.CharField(max_length=100, default='')
content = models.TextField()
rating = models.DecimalField(default=10.0, max_digits=5, decimal_places=2)
created_date = models.DateTimeField(default=timezone.now)
approved_venue = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
venue_category = models.ForeignKey(Category, on_delete=models.CASCADE, related_name='category')
def __str__(self):
return f"{self.title}"
class VenueFeatures:
seats = models.IntegerField()
bulgarian_kitchen = models.BooleanField(default=False)
italian_kitchen = models.BooleanField(default=False)
french_kitchen = models.BooleanField(default=False)
sea_food = models.BooleanField(default=False)
is_cash = models.BooleanField(default=False)
is_bank_card = models.BooleanField(default=False)
is_wi_fi = models.BooleanField(default=False)
is_garden = models.BooleanField(default=False)
is_playground = models.BooleanField(default=False)
is_fitness_trainer = models.BooleanField(default=False)
is_parts_clients = models.BooleanField(default=False)
is_hair_salon = models.BooleanField(default=False)
is_laser_epilation = models.BooleanField(default=False)
is_pizza = models.BooleanField(default=False)
is_duner = models.BooleanField(default=False)
is_seats = models.BooleanField(default=False)
is_external_cleaning = models.BooleanField(default=False)
is_internal_cleaning = models.BooleanField(default=False)
is_engine_cleaning = models.BooleanField(default=False)
is_working_weekend = models.BooleanField(default=False)
is_kids_suitable = models.BooleanField(default=False)
is_working_weekend = models.BooleanField(default=False)
venue = models.ForeignKey(Venue, on_delete=models.CASCADE, related_name='venue')
class Comment(models.Model):
venue = models.ForeignKey(Venue, on_delete=models.CASCADE, related_name='comments')
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
content = models.TextField()
rating = models.TextField()
approved_venue = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
created_date = models.DateTimeField(default=timezone.now)
def __str__(self):
return f"{self.content}"
class Images(models.Model):
venue = models.ForeignKey(Venue, default=None, on_delete=models.CASCADE)
image = models.ImageField(upload_to='attachments',
verbose_name='Image')
class VenueCoordinates(models.Model):
venue = models.ForeignKey(Venue, on_delete=models.CASCADE, related_name='coordinates')
latitude = models.CharField(max_length=60)
longitude = models.CharField(max_length=60)
Now I do not now how to use Venue with VenueFeatures
Notice that features are just true/false values (checkboxes in form).
Okay, this is probably the best way to abstract anything as much as I can:
from django.db import models
from users.models import ProfileUser
from django.utils import timezone
from polymorphic.models import PolymorphicModel
# Create your models here.
class City(models.Model):
name = models.CharField(max_length=20)
def __str__(self):
return f"{self.name}"
class Category(models.Model):
name = models.CharField(max_length=20)
bg_name = models.CharField(max_length=20, default=None)
category_bg_name = models.CharField(max_length=100, default=None)
icon = models.CharField(max_length=40, default=None)
def __str__(self):
return f"{self.name}"
class Venue(models.Model):
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
title = models.CharField(max_length=300)
city = models.ForeignKey(City, on_delete=models.CASCADE)
address = models.CharField(max_length=300)
phone = models.CharField(max_length=20, default='')
email = models.CharField(max_length=100, default='')
site = models.CharField(max_length=100, default='')
facebook = models.CharField(max_length=100, default='')
instagram = models.CharField(max_length=100, default='')
content = models.TextField()
rating = models.DecimalField(default=10.0, max_digits=5, decimal_places=2)
created_date = models.DateTimeField(default=timezone.now)
approved_venue = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
category = models.ForeignKey(Category, on_delete=models.CASCADE)
def __str__(self):
return f"{self.title}"
class Feature(models.Model):
name = models.CharField(max_length=100)
code = models.CharField(max_length=100 )
category = models.ForeignKey(Category, on_delete=models.CASCADE)
type = models.CharField(max_length=100)
def __str__(self):
return f"{self.name}"
class VenueFeatures(models.Model): # ManyToMany Venues <-> Features
venue = models.ForeignKey(Venue, on_delete=models.CASCADE)
feature = models.ForeignKey(Feature, on_delete=models.CASCADE)
value = models.CharField(max_length=255)
class Comment(models.Model):
venue = models.ForeignKey(Venue, on_delete=models.CASCADE, related_name='comments')
author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
content = models.TextField()
rating = models.TextField()
approved_venue = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
created_date = models.DateTimeField(default=timezone.now)
def __str__(self):
return f"{self.content}"
class Images(models.Model):
venue = models.ForeignKey(Venue, default=None, on_delete=models.CASCADE)
image = models.ImageField(upload_to='attachments',
verbose_name='Image')
class VenueCoordinates(models.Model):
venue = models.ForeignKey(Venue, on_delete=models.CASCADE, related_name='coordinates')
latitude = models.CharField(max_length=60)
longitude = models.CharField(max_length=60)
Now Features are bound with Categories
Also Venues are ManyToMany with Features
I have already linked it to business logic and it works fine.
TL;DR Use a JSONField (JSONB automatically I think) in PostgreSQL WITHOUT a GIN index for your VenueFeatures instead of creating an entirely new model. Postgres has come a long way towards NoSQL/unstructured DB and it's really good. Using a JSONField in your Venue model would work really well. At the very bottom, I talk about how I would design your site's db.
Although I hate saying this, but this could be the job of a NoSQL database. Usually every application uses RDBM which is structured, but you are using unstructured attributes. You could try using PostgreSQL's JSONB field but... stuffing everything into one field would be tiresome for the GIN index + caching.
For now, I'll ignore a lot of weird practices such as needing to partition a couple of attributes, max_length for char field is typically 255 length for all databases, making sure the most accessed tables don't have too many attributes so that caching is better (i.e. you don't have to invalidate your cache every time a user updates your table), GeoDjango for your coordinate system with the standard Mercator projection system on Postgres Geography mode, and you could use sets instead of dicts (sets are iterables and use {} but nothing is repeated)...
Stay away from this option: For one, I NEVER recommend MongoDB, but it could be useful for you... so long as your application doesn't grow too large as in a couple million records could break your system.
The other RECOMMENDED option is PostgreSQL's JSONB or Django's JSONField withOUT a GIN index (I strongly recommend you don't index this field since venues could change them sooo often to the point that REINDEXING and caching would burn your server and slow your app). It can be useful to store a venue's "Features" inside of this JSONB field since everything is super unstructured.
Lowering the number of attributes is better. You've got A LOT of them too which could slow down querying. I recommend you use Django-cachalot for caching since they support JSONField which can avoid your issue of having a LOT of attributes.
Other recommendations in general
Instead of using default='', just do blank=True, null=True since you're basically saying the user doesn't have to fill out the email field.
Kind of like how you would have a user profile instead of stuffing ALL of your attributes inside of the main User model, you want to partition your Venue data into different models.
The way I would've designed this:
Since you originally had these three venues, just make the "Categories" table into choices.
from django.contrib.gis.db import models # This also imports standard models
from django.contrib.postgres.fields import JSONField # Remember to turn on GeoDjango with PostgreSQL's PostGIS extension
from django.contrib.postgres.indexes import BrinIndex
class Venue(models.Model):
id = models.BigAutoField(primary_key=True)
title = models.CharField(max_length=255)
rating = models.DecimalField(default=10.0, max_digits=5, decimal_places=2)
created_date = models.DateTimeField(default=timezone.now)
approved_venue = models.BooleanField(default=False)
admin_seen = models.BooleanField(default=False)
VENUE_TYPES = [
(1, "restaurant"),
(2, "concert"),
(3, "art night")
]
category = SmallPositiveIntegerField(choices=VENUE_TYPES)
location = models.PointField(srid=4326) # mercator projection from GeoDjango. You don't have to use this; you can stick to your old city and address thing
class Meta:
indexes = (
BrinIndex(fields=['category']), # this is in case you have a LOT of categories later on.
)
class VenueProfile(models.Model):
venue = models.OneToOneField(Venue, on_delete=models.CASCADE, primary_key=True)
misc_features = JSONField() # This field is for stuff like your restaurant features OR your concert features. You can put whatever you want in there. Just make sure you have a list of features that people have when trying to access the JSON so you don't run into exceptions.
created_date = models.DateTimeField(auto_now_add=True)
facebook = models.CharField(max_length=100, blank=True, null=True)
instagram = models.CharField(max_length=100, blank=True, null=True)
city = models.ForeignKey(City, on_delete=models.SET_NULL, null=True) # SET_NULL in case you accidentally delete a city. You don't want to also delete the venue.
image = models.ImageField(upload_to='attachments',
verbose_name='Image')
# These attributes are universal for ANY venue so that's why they don't need to be in the JSONField
"""
For the rest of the features, I have no concern EXCEPT for city. Because you're using GeoDjango, you should also use MaxMind's free city database to determine location based on coordinates. That way, you've essentially scraped the need to store the user and such. You could probably save the address field since it could make things easier that a simple coordinate. It's really up to you. You could also use both!
"""
The attributes I've added to the Venue model are THE MOST important things in my opinion that a user would immediately want to know about.
The VenueFeature model is something that isn't updated that much. It's PRIME for using Django-cachalot to take over since it's not modified that often. (50 modifications per second makes invalidation of caches per modification a big hassle).
Comments model is fine.
As can be seen in the code below, I have an intermediate model that defines a custom date field. How can I reference the date_assigned field in the relation model. I am trying find the number of tenders that were assigned to the "user" (i.e. CompanyProfile) on a particular date as per the date_assigned field in the relation model. The CompanyProfile (i.e. user) model and the Tender model share one thing in common, they both have a relationship with the Keywords model through a ManyToMany relationship. This is how I am able to find Tenders allocated to the CompanyProfile through the Keywords model.
This is the final result I am aiming for.
class CompanyProfile(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
accountNumber = models.CharField(max_length=25, default=1, blank=False, null=False)
companyName = models.CharField(max_length=200, blank=False)
companyRegNum = models.CharField(max_length=30, blank=True)
contactNumber = models.CharField(max_length=20, blank=False)
address = models.CharField(max_length=300, blank=True)
areaCode = models.CharField(max_length=10, blank=False)
deliveryEmails = models.TextField(blank=True) #this is the list of all the people chosen to recieve daily notification.
tenderCategory = models.ManyToManyField(Category, blank=False) #links the user to the chosen category.
provinces = models.ManyToManyField(Province, blank=False) #links the user to the chosen Provinces.
package = models.ForeignKey(Packages, default=1, blank=False) #links the user to the chosen package.
pymntMethod = models.IntegerField(blank=True, default=3) #this is the chosen payment method (e.g credit card=1, debit order=2 or direct debit=3)
keywords = models.ManyToManyField(Keywords) #links the user to the chosen keywords.
extraKeywords = models.TextField(default='', blank=True) #this field acts as a container of extra keywords from the user. These are keywords that we do not have in our database.
contractDuration = models.IntegerField(blank=False, default=12)
termsAndConditions = models.BooleanField(blank=False, default=1) #this is the T&C's field that must be agreed to by the client.
commencementDate = models.DateTimeField(default=timezone.now, blank=True)
class Keywords(models.Model):
keyword = models.CharField(max_length=150)
class Meta:
verbose_name_plural = ('Keywords')
ordering = ['keyword', ]
def __str__(self):
return self.keyword
#This is the model that stores the 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.ForeignKey(Province, default=1, blank=False) #this is the province the tender was advertised from.
keywordTags = models.TextField(blank=False) #this field holds keywords for the tender as per the tender title or as determined by the tender capturer.
buyersName = models.CharField(max_length=100) #this is the name of the Buyer e.g. Dept. of Transport, Transnet, Dept of Agriculture etc.
summary = models.TextField(blank=False) #this is the tender title as per the Buyer.
refNum = models.CharField(max_length=100) #tender ref number as per the Buyer.
issueDate = models.DateTimeField(blank=True, null=True) #date the tender was published
closingDate = models.DateTimeField(blank=True, null=True) #tender closing date
siteInspection = models.TextField(blank=True, null=True) #site inspection date, if any
enquiries = models.TextField(blank=True, null=True) #this field stores details of the contact person, for the tender.
description = models.TextField(blank=True, null=True) #this is the body of the tender. the tender details are captured here.
assigned_keywords = models.ManyToManyField(Keywords, blank=True, through='tenderKeywords')
matched = models.BooleanField(default=0, blank=False)
capture_date = models.DateField(default=timezone.now, blank=False, null=False)
class TendersKeywords(models.Model):
tender = models.ForeignKey(tender, related_name='tender_keywords')
keyword = models.ForeignKey(Keywords, related_name='tender_keywords')
date_assigned = models.DateField(default=timezone.now, blank=False, null=False)
I am able to find the associated tenders for the CompanyProfile but I have a problem aggregating the results base on the tender issued_date which is defined in the relation model TendersKeywords.
The expected result you show is a model aggregation query. In particular, computing a count of matches grouped by a particular field, is a good use of the Count aggregation, applied to the queryset with an annotate operation.
import django.db
Tender.objects.values('issued').annotate(
tenders=django.db.models.Count('issued'))
What that does:
Use the Tender model manager (the Tender.objects attribute);
Use the values method to make a queryset containing just the issued field value;
Annotate that queryset with a field named tenders, that:
Has the value computed by the Count aggregate function for each group.
That all assumes a coherent model schema; I had to make some guesses (your code as presented doesn't work, please review the guidelines on creating a minimal, complete, verifiable example. In brief: Strip the example down to the minimum needed, and then actually run it to make sure it'll work for us too).
If you have an existing query and want to annotate that, then just apply the same technique:
existing_queryset.values('tender_issued').annotate(
tenders=django.db.models.Count('tender_issued'))
where tender_issued is whatever field in your queryset contains the value you want to group and count.
First, I want to modify your models
class tenderKeywords(models.Model):
tender = models.ForeignKey(tender, related_name='tenderkeywords')
keyword = models.ForeignKey(Keywords, related_name='tenderkeywords')
date_assigned = models.DateField(default=timezone.now, blank=False, null=False)
then:
count = tender.objects.filter(tenderKeywords__keyword__Keywords="", tenderKeywords__date_assigned= datetime)
Python developers have some standard in writing code. for example first letter of model's name should be capital. thanks for this.
I currently have two models set up in my Django app that have a ForeignKey relationship.
class Post(models.Model):
title = models.CharField(max_length=100)
body = RichTextField(config_name='awesome_ckeditor')
pub_date = models.DateTimeField('date', null=True)
description = models.CharField(max_length=100, blank=True, null=True)
photo = models.ImageField(upload_to='media/', blank=True, null=True)
def __unicode__(self):
return self.title
class Comment(models.Model):
post = models.ForeignKey(Post, related_name="comments", blank=True, null=True)
name = models.CharField(max_length=100, null=True)
comment = models.TextField(blank=True)
pub_date = models.DateField("date", blank=True, null=True)
def __unicode__(self):
return unicode(self.name)
What I am not getting is making queries between the two. I have tried making queries through the shell but to no success. If I set Post(title="Cat") and then make c = Comment(name="Dog"), I can query each models respective title or name through something like p = Post.object.get(pk=1) and p.title will output Cat. But if I do p.comment or p.comment_id, there is an error. Likewise with any Comment objects. However when I do print c.post, I get None. What am I missing in order to make p.<field_here>" =Dog`?
Since you have related name "comments", access to set foreign model from Post should be called this way:
p.comments
But since you can have many comments for a same Post, this won't return a unique value, but a related manager that you need to query. So you could get:
p.comments.filter(name="Dog")