#27332: Specifying additional ON arguments, and more flexibility with joins
-------------------------------------+-------------------------------------
Reporter: MikiSoft | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version:
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Nicolas Delaby):
Hi,
I started to look at this one and realized {{{GenericForeignKey}}}
implemented such functionnality in {{{ get_extra_restriction() }}}
https://github.com/django/django/blob/master/django/contrib/contenttypes/fields.py#L437
So I followed that path, and came up with a PoC implementation (with
passing tests), following this API:
{{{#!python
class ConditionalJoinTests(TestCase):
@classmethod
def setUpTestData(cls):
cls.author1 = Author.objects.create(name='Alice')
cls.author2 = Author.objects.create(name='Jane')
cls.book1 = Book.objects.create(title='Poem by Alice',
editor='A',
author=cls.author1)
cls.book2 = Book.objects.create(title='The book by Jane A',
editor='A',
author=cls.author2)
cls.book2 = Book.objects.create(title='The book by Jane B',
editor='B',
author=cls.author2)
def test_conditional_join_query_wo_join(self):
"""
All Authors are returned because no join is required by the
filters.
"""
self.assertQuerysetEqual(
Author.objects
.conditional_join('book', title__iexact='poem by alice'),
["<Author: Alice>", "<Author: Jane>"])
def test_conditional_join_query_with_join(self):
self.assertQuerysetEqual(
Author.objects
.conditional_join('book', title__iexact='poem by alice')
.filter(book__isnull=False),
["<Author: Alice>"])
self.assertQuerysetEqual(
Author.objects
.conditional_join('book', Q(title__iexact='poem by alice'))
.filter(book__isnull=False),
["<Author: Alice>"])
def test_conditional_join_query_with_join_multiple(self):
self.assertQuerysetEqual(
Author.objects
.conditional_join('book', title__icontains='jane', editor='B')
.filter(book__isnull=False),
["<Author: Jane>"])
}}}
If this proposal receives some interest, I'll be glad to work on preparing
a pull request to support this use case.
--
Ticket URL: <https://code.djangoproject.com/ticket/27332#comment:10>
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