Django Postgres JSONField query

Well first of all your JSON here is malformed. I presume it is meant to be:

[{'brand_id': 1, 'name': 'b1'}, {'brand_id': 2, 'name': 'b2'}] 

If that's the case, to test for 1 in such a blob, something like this will tell you if 1 is to be found anywhere in the JSON as a value:

def check_for_one(json_data):
    return any([1 in data.values() for data in json_data])

But you want to know specifically if 1 is a value owned by a key brand_id anywhere in the JSON so you can also use a loop to add in some extra conditions:

def check_for_one(json_data):
    match = []
    for data in json_data:
        for key, value in data.items():
            if key == 'brand_id' and value == 1:
                match.append(True)
    return any(match)

You can incorporate such logic as methods on your model class like this:

class A(models.Model):
    brand = JSONField()

    def check_for_one_comprehension(self):
        return any([1 in data.values() for data in self.brand])

    def check_for_one_loop(self):
        match = []
        for data in self.brand:
            for key, value in data.items():
                if key == 'brand_id' and value == 1:
                    match.append(True)
        return any(match)

But, if you actually want to filter instances from the database where the JSON data is an array at the top level and brand_id == 1, that needs a different approach, and this should do it:

A.objects.filter(brand__contains=[{'brand_id': 1}])

Note the additional [{}] braces! If you just call contains=['brand_id': 1] it will throw a syntax error and if you call contains={'brand_id': 1} it will not match.

This worked:

A.objects.filter(brands__contains=[{'brand_id':1}])

I didnt check it first by using the array. Link pointed put by @Bear Brown gives sufficient info. Its easy in django, but finding it out took time :P.