Django过滤器查询集返回外键值

Question

Here again with a Django question. I've got models as follows:

class Host(models.Model):
    id = models.IntegerField(primary_key=True)
    hostname = models.TextField()

    class Meta:
        managed = False
        db_table = 'py_hosts'

class Ip(models.Model):
    id = models.IntegerField(primary_key=True)
    ip = models.TextField()

    class Meta:
        managed = False
        db_table = 'py_ip'

class Port(models.Model):
    id = models.IntegerField(primary_key=True)
    port = models.TextField()

    class Meta:
        managed = False
        db_table = 'py_ports'

class Service(models.Model):
    id = models.IntegerField(primary_key=True)
    host = models.ManyToManyField("Host", through="HostService")
    ip = models.ManyToManyField("Ip", through="HostService")
    port = models.ManyToManyField("Port", through="HostService")
    service = models.TextField()

    class Meta:
        managed = False
        db_table = 'py_services'

    def __str__(self):
        return self.service

class HostService(models.Model):
    id = models.IntegerField(primary_key=True)
    host = models.ForeignKey(Host, on_delete=models.DO_NOTHING)
    ip = models.ForeignKey(Ip, on_delete=models.DO_NOTHING)
    port = models.ForeignKey(Port, on_delete=models.DO_NOTHING)
    service = models.ForeignKey(Service, on_delete=models.DO_NOTHING)

    class Meta:
        managed = False
        db_table = 'py_hostservices'

I also have the filter declared in filters.py using django-filters:

class ServiceFilter(django_filters.FilterSet):

    class Meta:
        model = Service
        fields = {
            'host': ['icontains',],
            'ip': ['icontains',],
            'service': ['icontains',],
            'port': ['icontains',],
        }

the filter is called in the view:

class ServiceListView(ListView):
    model = Service
    template_name = 'services/service_list.html'

    def get_context_data(self, **kwargs):

        context = super().get_context_data(**kwargs)
        context['filter'] = ServiceFilter(self.request.GET, queryset=self.get_queryset())
        return context

Finally, the html file where the filter is called:

<div class="container">

    <form method="GET">

        {{ filter.form }}
        <button type="submit" class="default" name="_save">Search</button>
    </form>

    <table border="1">
        <tbody>
            {% for service in filter.qs %}
            <tr>
                <td>{{ service.host }}</td>
                <td>{{ service.ip }}</td>
                <td>{{ service.service }}</td>
                <td>{{ service.port }}</td>
            </tr>
            {% endfor %}
        </tbody>
    </table>

</div>

Obviously the code won't work, but i can't understand how i should use Django ORM or filters to filter the queryset based on Foreign Key values and show Foreign Key values since the interim table is just used for linking Foreign Keys.

What i'd like to obtain is a queryset that outputs the equivalent of the following SQL:

SELECT a.description, b.description, c.description, d.description
  FROM py_hostservices
  JOIN py_services ON py_services.id = py_hostservices.service_id
  JOIN py_ports ON py_ports.id = py_hostservices.port_id
  JOIN py_ip ON py_ip.id = py_hostservices.ip_id
  JOIN py_hosts ON py_hosts.id = py_hostservices.host_id

Could you please give some insight on how I can develop this in Django?

UPDATE: Models, filters, views and html with new version.

Answer 1

Ok, sometimes simpler is better. Since i'm based on database views, i solved the design issue by creating the final view altogether in the database and then created a single model:

class HostService(models.Model):
    id = models.IntegerField(primary_key=True)
    hostname = models.TextField()
    ip = models.TextField()
    port = models.TextField()
    servicename = models.TextField()

    class Meta:
        managed = False
        db_table = 'py_hostservices'