Get distinct values of Queryset by field
I've got this model:
class Visit(models.Model):
timestamp = models.DateTimeField(editable=False)
ip_address = models.IPAddressField(editable=False)
If a user visits multiple times in one day, how can I filter for unique rows based on the ip field? (I want the unique visits for today)
today = datetime.datetime.today()
yesterday = datetime.datetime.today() - datetime.timedelta(days=1)
visits = Visit.objects.filter(timestamp__range=(yesterday, today)) #.something?
EDIT:
I see that I can use:
Visit.objects.filter(timestamp__range=(yesterday, today)).values('ip_address')
to get a ValuesQuerySet of just the ip fields. Now my QuerySet looks like this:
[{'ip_address': u'127.0.0.1'}, {'ip_address': u'127.0.0.1'}, {'ip_address':
u'127.0.0.1'}, {'ip_address': u'127.0.0.1'}, {'ip_address': u'127.0.0.1'}]
How do I filter this for uniqueness without evaluating the QuerySet and taking the db hit?
# Hope it's something like this...
values.distinct().count()
What you want is:
Visit.objects.filter(stuff).values("ip_address").annotate(n=models.Count("pk"))
What this does is get all ip_addresses and then it gets the count of primary keys (aka number of rows) for each ip address.
With Alex Answer I also have the n:1 for each item. Even with a distinct() clause.
It's weird because this is returning the good numbers of items :
Visit.objects.filter(stuff).values("ip_address").distinct().count()
But when I iterate over "Visit.objects.filter(stuff).values("ip_address").distinct()" I got much more items and some duplicates...
EDIT :
The filter clause was causing me troubles. I was filtering with another table field and a SQL JOIN was made that was breaking the distinct stuff. I used this hint to see the query that was really used :
q=Visit.objects.filter(myothertable__field=x).values("ip_address").distinct().count()
print q.query
I then reverted the class on witch I was making the query and the filter to have a join that doesn't rely on any "Visit" id.
hope this helps
The question is different from what the title suggests. If you want set-like behavior from the database, you need something like this.
x = Visit.objects.all().values_list('ip_address', flat=True).distinct()
It should give you something like this for x
.
[1.2.3.4, 2.3.4.5, ...]
Where
len(x) == len(set(x))
Returns True