One QuerySet for two tables (one to many related) - django

Question

I have created one to many relationship (two tables) such that every user has its own IP connections list. Every user has many connections.
My models are shown below:
class Conn(models.Model):
src_ip = models.CharField(max_length=18, unique=False,default=None,blank=True,null=True)
src_port = models.CharField(max_length=6, unique=False,default=None,blank=True,null=True)
dst_ip = models.CharField(max_length=18, unique=False,default=None,blank=True,null=True)
dst_port = models.CharField(max_length=6, unique=False,default=None,blank=True,null=True)
proto = models.CharField(max_length=6, unique=False,default=None,blank=True,null=True)
start_data = models.CharField(max_length=18, unique=False,default=None,blank=True,null=True)
r_user = models.ForeignKey(User, on_delete=models.CASCADE)
class User(models.Model):
e_user = models.CharField(max_length=15, unique=False,default=None,blank=True,null=True)
e_dev = models.CharField(max_length=15, unique=False,default=None,blank=True,null=True)
e_session = models.CharField(max_length=9, unique=False,default=None,blank=True,null=True)
e_start = models.CharField(max_length=20, unique=False,default=None,blank=True,null=True)
e_stop = models.CharField(max_length=20, unique=False,default=None,blank=True,null=True)
e_summary = models.CharField(max_length=20, unique=False,default=None,blank=True,null=True)
e_ip = models.CharField(max_length=20, unique=False,default=None,blank=True,null=True)
I'm trying to get all Users with their connections (Conn) in one QuerySet and then display everything in template. So far I can display every User without any problems with
q=Users.objects.all()
and passing the QuerySet to the template.
The question may be a bit not smart but how can I query all Users including related connections (Conn) as one QuerySet and then enumerate this connections in a form?

Answer 1

Use prefetch_related:
users = User.objects.all().prefetch_related('conn_set')
Now for each user you can look at its conn_set and see the Conn objects linked to it. Assuming you pass users to your template as a context variable users, something like this should work:
{% for user in users %}
{{ user.e_user }}
{% for connection in user.conn_set.all }}
{{ connection.src_ip }}
{% endfor %}
{% endfor %}
Adjust fields and add other markup to suit your needs.
From the documentation, prefetch_related
Returns a QuerySet that will automatically retrieve, in a single batch, related objects for each of the specified lookups.
If this had been a one-to-one relationship or if you'd been trying to look things up in the other direction, finding all Conn objects along with the related User, you could have used select_related, which is even more efficient.
Note that you can also clean up some of your fields by choosing more appropriate field types. For example, consider GenericIPAddressField for src_ip and dst_ip.