Chain together multiple (disparate) QuerySets to treat them as a single QuerySet.
Project description
The QuerySetSequence wrapper helps to deal with disparate QuerySet classes, while treating them as a single QuerySet.
Supported Features
filter() / exclude() / get() across fields common to all sub-QuerySets.
order_by() fields common across all sub-QuerySets. Includes ordering by fields of related models (e.g. 'foo__bar' syntax), and ordering of related fields (e.g. 'foo', or 'foo_id'). syntax).
len() / count() to get the total length across all QuerySets.
Slicing and indexing works as expected.
QuerySetSequence is an iterable.
QuerySets are evaluated as late as possible.
Known Issues
Cannot handle random order_by()``(e.g. ``order_by('?')).
The fully QuerySet API is not complete.
Requirements
Python (2.7)
Django (1.8, 1.9)
Support for Python (3.3, 3.4, 3.5) is wanted. If you wish an older version of Django to be supported, please submit a pull request.
Installation
Install the package using pip.
pip install --upgrade django-querysetsequence
Usage
# Import QuerySetSequence
from queryset_sequence import QuerySetSequence
# Create QuerySets you want to chain.
from .models import SomeModel, OtherModel
# Chain them together.
query = QuerySetSequence(SomeModel.objects.all(), OtherModel.objects.all())
# Use query as if it were a QuerySet! E.g. in a ListView.
Example
class Author(models.Model):
name = models.CharField(max_length=50)
class Meta:
ordering = ['name']
def __str__(self):
return self.name
class Article(models.Model):
title = models.CharField(max_length=100)
author = models.ForeignKey(Author)
def __str__(self):
return "%s by %s" % (self.title, self.author)
class Book(models.Model):
title = models.CharField(max_length=50)
author = models.ForeignKey(Author)
release = models.DateField(auto_now_add=True)
def __str__(self):
return "%s by %s" % (self.title, self.author)
# Create some data.
alice = Author.objects.create(name='Alice')
article = Article.objects.create(title='Dancing with Django', author=alice)
bob = Author.objects.create(name='Bob')
article = Article.objects.create(title='Django-isms', author=bob)
article = Book.objects.create(title='Biography', author=bob)
# Create some QuerySets.
books = Book.objects.all()
articles = Article.objects.all()
# Combine them into a single iterable.
published_works = QuerySetSequence(books, articles)
# Find Bob's titles.
bob_works = published_works.filter(author=bob)
# Still an iterable.
print([w.title for w in bob_works]) # prints: ['Biography', 'Django-isms']
# Alphabetize the QuerySet.
published_works = published_works.order_by('title')
print([w.title for w in published_works]) # prints ['Biography', 'Dancing with Django', 'Django-isms']
Attribution
This is based on a few DjangoSnippets that had been going around:
Originally from https://www.djangosnippets.org/snippets/1103/
Modified version from https://djangosnippets.org/snippets/1253/
Upgraded version from https://djangosnippets.org/snippets/1933/
Updated version from django-ko-demo from The Atlantic
Contribute
Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug.
Fork the repository on GitHub to start making your changes.
Write a test which shows that the bug was fixed or that the feature works as expected.
Send a pull request and bug the maintainer until it gets merged and published.
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