Chain together multiple (disparate) QuerySets to treat them as a single QuerySet.
The QuerySetSequence wrapper helps to deal with disparate QuerySet classes, while treating them as a single QuerySet.
Listed below are features of Django’s QuerySets that QuerySetSequence implements. The behavior should match that of QuerySet, but applied across multiple QuerySets:
| Method | Implemented? | Notes |
|---|---|---|
| filter() | ✓ | See [1] for information on the QuerySet lookup: '#'. |
| exclude() | ✓ | See [1] for information on the QuerySet lookup: '#'. |
| annotate() | ✗ | |
| order_by() | ✓ | Does not support random ordering (e.g. order_by('?')). See [1] for information on the QuerySet lookup: '#'. |
| reverse() | ✓ | |
| distinct() | ✗ | |
| values() | ✗ | |
| values_list() | ✗ | |
| dates() | ✗ | |
| datetimes() | ✗ | |
| none() | ✓ | |
| all() | ✓ | |
| select_related() | ✓ | |
| prefetch_related() | ✓ | |
| extra() | ✗ | |
| defer() | ✗ | |
| only() | ✗ | |
| using() | ✗ | |
| select_for_update() | ✗ | |
| raw() | ✗ | |
| get() | ✓ | See [1] for information on the QuerySet lookup: '#'. |
| create() | ✗ | Cannot be implemented in QuerySetSequence. |
| get_or_create() | ✗ | Cannot be implemented in QuerySetSequence. |
| update_or_create() | ✗ | Cannot be implemented in QuerySetSequence. |
| bulk_create() | ✗ | Cannot be implemented in QuerySetSequence. |
| count() | ✓ | |
| in_bulk() | ✗ | Cannot be implemented in QuerySetSequence. |
| iterator() | ✓ | |
| latest() | ✗ | |
| earliest() | ✗ | |
| first() | ✗ | |
| last() | ✗ | |
| aggregate() | ✗ | |
| exists() | ✓ | |
| update() | ✗ | Cannot be implemented in QuerySetSequence. |
| delete() | ✓ | |
| as_manager() | ✓ |
| [1] | (1, 2, 3, 4) QuerySetSequence supports a special field lookup that looks up the index of the QuerySet, this is represented by '#'. This can be used in any of the operations that normally take field lookups (i.e. filter(), exclude(), and get()), as well as order_by(). A few examples are below: # Order first by QuerySet, then by the value of the 'title' field. QuerySetSequence(...).order_by('#', 'title') # Filter out the first QuerySet. QuerySetSequence(...).filter(**{'#__gt': 0}) Note Ordering first by QuerySet allows for a more optimized code path when iterating over the entries. Warning Not all lookups are supported when using '#' (some lookups simply don’t make sense; others are just not supported). The following are allowed:
|
| Django 1.8 | Django 1.9 | Django 1.10 | |
|---|---|---|---|
| Django REST Framework 3.2 | 0.7 | ✗ | ✗ |
| Django REST Framework 3.3 | 0.7 | 0.7 | ✗ |
| Django REST Framework 3.4 | 0.7 | 0.7 | 0.7 |
Install the package using pip.
pip install --upgrade django-querysetsequence
# 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.
You can also provide a model keyword argument if you need to specify the QuerySet Model, e.g. for compatibility with some third-party applications that check the model field for equality
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']
django-querysetsequence comes with a custom CursorPagination class that helps integration with Django REST Framework. It is optimized to iterate over a QuerySetSequence first by QuerySet and then by the normal ordering configuration. This uses the optimized code-path for iteration that avoids interleaving the individual QuerySets. For example:
from queryset_sequence.pagination import SequenceCursorPagination class PublicationPagination(SequenceCursorPagination): ordering = ['author', 'title'] class PublicationViewSet(viewsets.ModelViewSet): pagination_class = PublicationPagination def get_queryset(self): # This will return all Books first, then all Articles. Each of those # is individually ordered by ``author``, then ``title``. return QuerySetSequence(Book.objects.all(), Article.objects.all())
This is based on a few DjangoSnippets that had been going around:
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
| File Name & Checksum SHA256 Checksum Help | Version | File Type | Upload Date |
|---|---|---|---|
| django_querysetsequence-0.7.2-py2.py3-none-any.whl (33.9 kB) Copy SHA256 Checksum SHA256 | py2.py3 | Wheel | Apr 4, 2017 |
