Combining multiple filters on querysets with django-filter

Question

Say, I have the following two Django models:

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    name = models.CharField(max_length=300)
    pages = models.IntegerField()
    author = models.ForeignKey(Author)

With django-filter, how can I write a FilterSet, that allows me to filter somewhat like:

Author.objects.filter(
    (Q(book__name__contains='How') & Q(book__pages=100)) |
    (Q(book__name__contains='Why') & Q(book__pages=50))
)

That is, I want to have a set of filter Fields, that are all applied to a related model and that I can combine. In my case, that set contains many more fields, so a custom MultiValueField is probably not really applicable.

Is there any standard way to solve this using django-filter, or should I implement my own filtering logic in the view?

What would the request querystring look like here? How would you differentiate the two sets of Q objects that you want to filter by? — Sherpa
– Sherpa, Commented Nov 16, 2016 at 3:23
?book_name_1=How&book_pages_2=100&book_name_2=why&book_pages_2=50 — janoliver
– janoliver, Commented Nov 16, 2016 at 7:37

Carlton Gibson · Accepted Answer · 2016-11-16 08:41:53Z

2

If you want to keep this in the FilterSet, rather than pushing back up to the view, your best bet is to override the qs property and add the multi-value filtering logic there.

(A field with a custom method provides validation but still only takes a single value — so you'd need to pull the others from the parent anyway — as such, overriding qs seems clearer.)

answered Nov 16, 2016 at 8:41

Carlton Gibson

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2 Comments

janoliver Over a year ago

I thought so, and decided that just doing it manually in the view with a standard django form would be an easier and more readable solution. However, your answer is still the correct way to go with django-filter, so I'll accept it.

Carlton Gibson Over a year ago

Yep, fair enough. Django Filter's scope is "common filtering problems" — uncommon ones may still require doing it by hand. :-)

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