django-join-unrelated

Use SQL Join with Django ORM models having no relations.

If you have models in your project that share the same data but have no relations, you might face a situation when you need to join them. But Django does not provide this functionality yet.

With django-join-unrelated you can do the following (models defined here):

from app.core.models import Jedi, Person

Person.objects.create(first_name='Padme', last_name='Amidala', birth_place='Naboo')
Person.objects.create(first_name='Obi-Wan', last_name='Kenobi', birth_place='Stewjon')
Jedi.objects.create(first_name='Obi-Wan', last_name='Kenobi', force=100)
Jedi.objects.create(first_name='Mace', last_name='Windu', force=80)

Jedi.objects.join(first_name=Person.first_name).values_list('first_name')
# <UnrelatedJoinQuerySet [('Obi-Wan',)]>

print(Jedi.objects.join(first_name=Person.first_name).values_list('first_name').query)
# SELECT "core_jedi"."first_name" FROM "core_jedi" INNER JOIN core_person ON ("core_jedi"."first_name" = core_person."first_name")

# Set join type explicitly
from django_join_unrelated import JoinType

Jedi.objects.join(first_name=Person.first_name, join_type=JoinType.FULL)

# Join on multiple fields
Jedi.objects.join(first_name=Person.first_name, last_name=Person.last_name)

# Join multiple models
Jedi.objects.join(first_name=Person.first_name, id=User.id)

django-join-unrelated tries to keep all QuerySet power where it is possible:

Jedi.objects.join(first_name=Person.first_name).filter(last_name='Kenobi')
# <UnrelatedJoinQuerySet [<Jedi: Obi-Wan Kenobi>]>

Jedi.objects.join(first_name=Person.first_name).annotate(name=F('first_name'))[0].name
# 'Obi-Wan'

Jedi.objects.join(first_name=Person.first_name).aggregate(Sum('force'))
# {'force__sum': 100}

Installation

You can install django-join-unrelated using pip:

pip install django-join-unrelated

Usage

Just import UnrelatedJoinManager and set it as an attribute to your models:

from django.db import models
from django_join_unrelated import UnrelatedJoinManager

class Jedi(models.Model):
    first_name = models.CharField('First name', max_length=128)
    last_name = models.CharField('Last name', max_length=128)
    force = models.IntegerField('Force')

    objects = UnrelatedJoinManager()

    class Meta:
        verbose_name = 'Jedi'

Already implemented:

• filtering via joins

Not implemented yet but planned:

• unrelated objects selection
• return of joined values