Count number of records by date in Django


Question

I have a model similar to the following:

class Review(models.Model):
    venue = models.ForeignKey(Venue, db_index=True)
    review = models.TextField()  
    datetime_created = models.DateTimeField(default=datetime.now)

I'd like to query the database to get the total number of reviews for a venue grouped by day. The MySQL query would be:

SELECT DATE(datetime_created), count(id) 
FROM REVIEW 
WHERE venue_id = 2
GROUP BY DATE(datetime_created);

What is the best way to accomplish this in Django? I could just use

Review.objects.filter(venue__pk=2)

and parse the results in the view, but that doesn't seem right to me.

1
48
12/19/2015 8:50:58 AM

Accepted Answer

This should work (using the same MySQL specific function you used):

Review.objects.filter(venue__pk=2)
    .extra({'date_created' : "date(datetime_created)"})
    .values('date_created')
    .annotate(created_count=Count('id'))
86
6/13/2014 9:46:14 PM

Just for completeness, since extra() is aimed for deprecation, one could use this approach:

from django.db.models.expressions import DateTime

Review.objects.all().\
    annotate(month=DateTime("timestamp", "month", pytz.timezone("Etc/UTC"))).\
    values("month").\
    annotate(created_count=Count('id')).\
    order_by("-month")

It worked for me in django 1.8, both in sqlite and MySql databases.


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