Django filter queryset __in for *every* item in list

Question

Let's say I have the following models

class Photo(models.Model):
    tags = models.ManyToManyField(Tag)

class Tag(models.Model):
    name = models.CharField(max_length=50)

In a view I have a list with active filters called categories. I want to filter Photo objects which have all tags present in categories.

I tried:

Photo.objects.filter(tags__name__in=categories)

But this matches any item in categories, not all items.

So if categories would be ['holiday', 'summer'] I want Photo's with both a holiday and summer tag.

Can this be achieved?

Answer 1

Another approach that works, although PostgreSQL only, is using django.contrib.postgres.fields.ArrayField:

Example copied from docs:

>>> Post.objects.create(name='First post', tags=['thoughts', 'django'])
>>> Post.objects.create(name='Second post', tags=['thoughts'])
>>> Post.objects.create(name='Third post', tags=['tutorial', 'django'])

>>> Post.objects.filter(tags__contains=['thoughts'])
<QuerySet [<Post: First post>, <Post: Second post>]>

>>> Post.objects.filter(tags__contains=['django'])
<QuerySet [<Post: First post>, <Post: Third post>]>

>>> Post.objects.filter(tags__contains=['django', 'thoughts'])
<QuerySet [<Post: First post>]>

ArrayField has some more powerful features such as overlap and index transforms.

Answer 2

This also can be done by dynamic query generation using Django ORM and some Python magic :)

from operator import and_
from django.db.models import Q

categories = ['holiday', 'summer']
res = Photo.filter(reduce(and_, [Q(tags__name=c) for c in categories]))

The idea is to generate appropriate Q objects for each category and then combine them using AND operator into one QuerySet. E.g. for your example it'd be equal to

res = Photo.filter(Q(tags__name='holiday') & Q(tags__name='summer'))

Answer 3

I use a little function that iterates filters over a list for a given operator an a column name :

def exclusive_in (cls,column,operator,value_list):         
    myfilter = column + '__' + operator
    query = cls.objects
    for value in value_list:
        query=query.filter(**{myfilter:value})
    return query  

and this function can be called like that:

exclusive_in(Photo,'tags__name','iexact',['holiday','summer'])

it also work with any class and more tags in the list; operators can be anyone like 'iexact','in','contains','ne',...

Answer 4

If you struggled with this problem as i did and nothing mentioned helped you, maybe this one will solve your issue

Instead of chaining filter, in some cases it would be better just to store ids of previous filter

tags = [1, 2]
for tag in tags:
    ids = list(queryset.filter(tags__id=tag).values_list("id", flat=True))
    queryset = queryset.filter(id__in=ids)

Using this approach will help you to avoid stacking JOIN in SQL query:

Answer 5

My solution: let say author is list of elements that need to match all item in list, so:

        for a in author:
            queryset = queryset.filter(authors__author_first_name=a)
                if not queryset:
                    break

Answer 6

for category in categories:
    query = Photo.objects.filter(tags_name=category)

this piece of code , filters your photos which have all the tags name coming from categories.

Answer 7

If we want to do it dynamically, followed the example:

tag_ids = [t1.id, t2.id]
qs = Photo.objects.all()

for tag_id in tag_ids:
    qs = qs.filter(tag__id=tag_id)    

print qs

Answer 8

queryset = Photo.objects.filter(tags__name="vacaciones") | Photo.objects.filter(tags__name="verano")