Query on a Many to Many relationship using through in Django - django

Question

I'm new in Django and I'm giving myself a big headhache trying to structure this query.
I have a BaseProfile connected with a OneToOne field to User.
I'm specializing the profile in CustomerProfile connected with a OneToOne field to BaseProfile.
A CustomerProfile has a ManyToMany relationship with other CustomerProfile (so itself) through a RelatedCustomer model.
In the RelatedCustomer I specify the from_customer and to_customer Foreign Keys.
Maybe with an image you can understand better.
My problem:
Given a user.id I need to know all the other user.id of the customers that he is connected to (so passing through from_customer and to_customer):
So basically, first I need to dig from User to RelatedCustomer using reverse lookup, take all the set, and then going back to know the user.id of each customer in the set.
EDIT2:
What I've reached so far:
# This gives me back a customer profile given a user.id (2)
cm = CustomerProfile.objects.get(base_profile__user=2)
# M2M lookup. Given one customer returns all the RelatedCustomer relations
# that he has as a part of the 'from' M2M
cm.from_photographer.all()
Chaining the previous two: given a user.id I obtain a queryset of CustomerRelated relations:
rel = CustomerProfile.objects.get(base_profile__user=2).from_photographer.all()
This gives me back something like:
[<CustomerRelated: from TestCustomer4 to TestCustomer2 >,
<CustomerRelated: from TestCustomer4 to TestCustomer3 >]
Where in this case the user having a user.id=2 is the TestCustomer4.
My question:
So far so good, but now having this set how can I get all the user.id of the to_customer?
That is, how do I get the user.id of TestCustomer2 and TestCustomer3?

Answer 1

Firstly, this is not how you query the database in django. Secondly (since you're learning), it would be good to point out that you can run dbshell to try out different things. And lastly, this kind of problem is described in the documentation.
I am telling you this, because as a beginner, I also felt that it was a little difficult to navigate through the whole thing. The best way to find things is just to use google, and add a django at the end.
I know how you feel, the documentation search sucks, right? Heh, I feel you, that is why you always search the way I described it. Once you get a hang of the documentation, you will feel that the documentation title page is a little more intuitive.
Okay, so now to the answer:
To access a ManyToMany, OneToOne or ForeignKey field, you need to use a __ commonly known as dunder.
So, this is how I would go about doing this. Please note that there are other ways, and potentially better ways of doing this:
thing_I_want = RelatedCustomer.objects.get(to_customer__id=2)
Note, however that if you wanted to get a list of customers you would use filter(). Here is an example (which uses number of purchases as an example):
things_I_want = RelatedCustomer.objects.filter(to_customer__no_of_purchases=16)
Also note that the great thing about filter is that you stack one filter on top of another. You can read more about these features in the documentation link I provide below.
That will get you what you want. Now, you might have more queries regarding this, and how it all works together. Not to fear, please click this documentation link to check it out.
EDIT
Seems like what you want to do can be done by django, but if you want to do it using sql, then that is possible too. For example, SomeModel.objects.raw("SQL_HERE"). The name of the tables are usually <app>_<model>.
However, what you are asking can also be done in django, using the ORM. But it will be tricky.

Answer 2

Ok, as usual whenever you get the answer it always look much more easier than what you were expecting.
I guess this worked for me:
User.objects.filter(base_profile__customer_profile__to_customer__in=
User.objects.get(id=2).base_profile.customer_profile.from_customer.all())
Many thanks to #Games Brainiac