Nested Filters

[ben.stookey@…]

After review in #django I decided to post this as a bug.

3 and 4 should have the same output, shouldn't they?

>>> Article.objects.filter(tags=t1)   #1
[<Article: A1>, <Article: A2>]
>>> Article.objects.filter(tags=t2)   #2
[<Article: A1>]
>>> Article.objects.filter(tags=t1).filter(tags=t2)   #3
[]
>>> Article.objects.filter(tags=t1, tags=t2)   #4
[<Article: A1>]

Although 4 works, the syntax doesn't allow for someone working with a list of tags.

Here are the models:

class Tag(models.Model):
	name = models.CharField(maxlength=32, unique=True)

class Article(models.Model):
	title = models.CharField(maxlength=255)
	tags = models.ManyToManyField(Tag)

[ben.stookey@…]

I guess 4 wasn't actually working either because I can't pass "tags" twice. It only looked at t2:

>>> Article.objects.filter(tags=t2, tags=t1)
[<Article: A1>, <Article: A2>]

[nick.lane.au@…]

As you said, Article.objects.filter(tags=t2, tags=t1) won't work because you can't pass duplicate keyword arguments for "tags". For this you could use:

>>> Article.objects.filter(tags__in=(t1, t2)).distinct()
[<Article: A1>, <Article: A2>]

[ben.stookey@…]

The problem is, that is an OR relationship and I'm looking for AND. Only those articles that have both tags. Shouldn't number 3 do that?

[nick.lane.au@…]

Sorry, I see what you mean now.

[Malcolm Tredinnick]

This is a known bug. I thought it was a duplicate of something, but I can't find it now. I'm back to working on the QuerySet rewrite, so it's something that gets fixed as part of that. Conjunctions involving the same column do not work at the moment.

[Malcolm Tredinnick]

Dupe of #4464.