django-queryset – Page 2

Limiting Memory Use in a Large Django QuerySet

December 9, 2023 by Tarik

What about using django core’s Paginator and Page objects documented here: https://docs.djangoproject.com/en/dev/topics/pagination/ Something like this: from django.core.paginator import Paginator from djangoapp.models import SomeModel paginator = Paginator(SomeModel.objects.all(), 1000) # chunks of 1000 for page_idx in range(1, paginator.num_pages): for row in paginator.page(page_idx).object_list: # here you can do what you want with the row print “done processing page … Read more

JSON Serializing Django Models with simplejson

December 2, 2023 by Tarik

I would go with extending simplejson. Basically, you want to plug in django’s serialization when the JSON encoder encounters a QuerySet. You could use something like: from json import dumps, loads, JSONEncoder from django.core.serializers import serialize from django.db.models.query import QuerySet from django.utils.functional import curry class DjangoJSONEncoder(JSONEncoder): def default(self, obj): if isinstance(obj, QuerySet): # `default` must … Read more

Use “contains” and “iexact” at the same query in DJANGO

November 30, 2023 by Tarik

If you need case-insensitive contains, use icontains: casas = Casa.objects.filter(nome_fantasia__icontains=”green”) Which is converted to … WHERE nome_fantasia ILIKE ‘%green%’ in SQL.

What is the correct way of returning an empty queryset in a Django View?

November 30, 2023 by Tarik

I think the best way to accomplish this is to call none() on objects for your respective model, and return the result. Assuming your model is named Entry: queryset = Entry.objects.none()

How to dynamically provide lookup field name in Django query? [duplicate]

November 30, 2023 by Tarik

I would prefer to use the Q object for something like this. from django.db.models import Q keyword = ‘keyword’ fields = [‘foo’, ‘bar’, ‘baz’] Qr = None for field in fields: q = Q(**{“%s__contains” % field: keyword }) if Qr: Qr = Qr | q # or & for filtering else: Qr = q # … Read more

QuerySet, Object has no attribute id – Django

November 27, 2023 by Tarik

this line of code at = AttachedInfo.objects.filter(attachedMarker=m.id, title=title) returns a queryset and you are trying to access a field of it (that does not exist). what you probably need is at = AttachedInfo.objects.get(attachedMarker=m.id, title=title)

Django: does the ORM support the SQL “IN” operator?

November 26, 2023 by Tarik

in User.objects.filter(id__in=[1, 5, 34, 567, 229]) print _.query SELECT <fields> FROM “auth_user” WHERE “auth_user”.”id” IN (1, 5, 34, 567, 229)

In Django, can you add a method to querysets?

November 26, 2023 by Tarik

As of django 1.7, the ability to use a query set as a manager was added: class PersonQuerySet(models.QuerySet): def authors(self): return self.filter(role=”A”) def editors(self): return self.filter(role=”E”) class Person(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) role = models.CharField(max_length=1, choices=((‘A’, _(‘Author’)), (‘E’, _(‘Editor’)))) people = PersonQuerySet.as_manager() Resulting the following: Person.people.authors(last_name=”Dahl”) In addition, the ability to add custom … Read more

How to seed Django project ? – insert a bunch of data into the project for initialization

November 21, 2023 by Tarik

Similar to Rails, we also have option to seed the database. It is done using management commands. In one of your apps, use the following folder structure <project>/<app>/management/commands/seed.py this makes python manage.py seed available as a management command. I personally follow the following structure. # <project>/<app>/management/commands/seed.py from django.core.management.base import BaseCommand import random # python manage.py … Read more

Django equivalent of COUNT with GROUP BY

September 28, 2023 by Tarik

If you are using Django 1.1 beta (trunk): Player.objects.values(‘player_type’).order_by().annotate(Count(‘player_type’)) values(‘player_type’) – for inclusion only player_type field into GROUP BY clause. order_by() – for exclusion possible default ordering that can cause not needed fields inclusion in SELECT and GROUP BY.