Django model aggregate matches count in ManyToMany

Question

There is Model with ManyToMany field:

class Number(Model):
    current_number = IntegerField()

class MyModel(models.Model):
    numbers_set = models.ManyToMany(Number)

For example we have such dataset:

my_model_1.numbers_set = [1, 2, 3, 4]
my_model_2.numbers_set = [2, 3, 4, 5]
my_model_3.numbers_set = [3, 4, 5, 6]
my_model_4.numbers_set = [4, 5, 6, 7]
my_model_5.numbers_set = [4, 5, 6, 7]

I'm looking for a way to aggregate MyModel by amount of same numbers.

f.e. MyModel objects that have at least 3 same numbers in theirs numbers_set.

[
    [my_model_1, my_model_2],
    [my_model_2, my_model_3],
    [my_model_3, my_model_4, my_model_5],
]

What if more than two models have at least 3 same numbers? Do you want all of them in the same list? — AKS, May 11 '16 at 05:48
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/111597/discussion-between-alex-t-and-aks). — Alex T, May 11 '16 at 06:10
Note: Since you're using Postgres, you may be able to just use an [`ArrayField`](https://docs.djangoproject.com/en/1.9/ref/contrib/postgres/fields/#arrayfield) — Sayse, May 11 '16 at 06:24
@Sayse, thanks. But it's just very general example, of course in my case it's not just int values. — Alex T, May 11 '16 at 06:27

score 0 · Answer 1 · answered May 11 '16 at 10:45

0

if you are using Postgres version 9.4 and Django version 1.9 , It's better to use JSONField() rather than using ManyToMany(), for indexing purpose use jsonb indexing on Postgres which will provide you efficient query for fetching data. Check here

answered May 11 '16 at 10:45

Piyush S. Wanare

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In real case instead of Number I have quite common model with various fields (TextField, CharField, DateTimeField, IntegerField). So I assume I can't use JSONField.. – Alex T May 11 '16 at 13:37

Django model aggregate matches count in ManyToMany

1 Answers1