"Matching"/relations data across databases in Django

Question

In developing a website for indexing system documentation I've come across a tough nut to crack regarding data "matching"/relations across databases in Django.

A simplified model for my local database:

from django.db import models

class Document(models.Model):
    name = models.CharField(max_length=200)
    system_id = models.IntegerField()
    ...

Imagined model, system details are stored in a remote database.

from django.db import models               

class System(models.Model):     
    name = models.CharField(max_length=200)           
    system_id = models.IntegerField()      
    ...

The idea is that when creating a new Document entry at my website the ID of the related system is to be stored in the local database. When presenting the data I would have to use the stored ID to retrieve the system name among other details from the remote database.

I've looked into foreign keys across databases, but this seems to be very extensive and I'm not sure if I want relations. Rather I visualize a function inside the Document model/class which is able to retrieve the matching data, for example by importing a custom router/function.

How would I go about solving this?

---

Note that I won't be able to alter anything on the remote database, and it's read-only. Not sure if I should create a model for System aswell. Both databases use PostgreSQL, however my impression is that it's not really of relevance to this scenario which database is used.

Answer 1

In the django documentation multi-db (manually-selecting-a-database)

# This will run on the 'default' database.
Author.objects.all()

# So will this.
Author.objects.using('default').all()

# This will run on the 'other' database.
Author.objects.using('other').all()

The 'default' and 'other' are aliases for you databases.
In your case it would could be 'default' and 'remote'.

of course you could replace the .all() with anything you want.

Example: System.objects.using('remote').get(id=123456)