Django: Sort query with common column value

Hey, Let's say I have this model:

class Log:
 msg = CharField(...)
 project = ForeignKey(..)
 date = DateField(..)

Now let's say I want to select the 4 most recent logs:

 logs = Log.objects.order_by('project').order_by('-date')[:4]

Further, I want to extract the logs that share the same 开发者_如何学运维project so in my template, I'd like to do something like:

 {% for proj in projects %}
   [Do something with the proj model instance]
   {% for log in proj.logs(?) %}
     [Do something with logs]
   {% endfor %}
 {% endfor %}

How to?

In your template you could regroup by project.

From the docs something (untested) like

{% regroup logs|dictsort:"project.id" by project as project_list %}

{% for project in project_list %}
    {{ project.grouper }}
        {% for item in project.list %}
            [Do something with logs]
        {% endfor %}
{% endfor %}

{% for proj in projects %}
  {{ proj.name }}
  {% for log in proj.log_set.all %}
    {{ log.msg }}
  {% endfor %}
{% endfor %}

If you use a related_name for your ForeignKey (let's say "logs") you could you could use proj.logs instead of proj.log_set. Check the docs.

If you need the latest logs for a project on a regular basis i'd consider writing a method for your Project model:

def recent_logs(self):
    return self.log_set.all()[:4]

Then you could adjust the loop in your template to:

{% for log in proj.recent_logs %}
    {{ log.msg }}
{% endfor %}