Hi, Django rookie here.
I have this model, comments are managed with the django_comments contrib:
class Fortune(models.Model):
author = models.CharField(max_length=45, blank=False)
title = models.CharField(max_length=200, blank=False)
slug = models.SlugField(_('slug'), db_index=True, max_length=255, unique_for_date='pub_date')
content = models.TextField(blank=False)
pub_date = models.DateTimeField(_('published date'), db_index=True, default=datetime.now())
votes = models.IntegerField(default=0)
comments = generic.GenericRelation(
Comment,
content_type_field='content_type',
object_id_field='object_pk'
)
I want to retrieve Fortune objects with a supplementary nb_comments value for each, counting their respectve number of comments ; I try this query:
>>> Fortune.objects.annotate(nb_comments=models.Count('comments'))
From the shell:
>>> from django_fortunes.models import Fortune
>>> from django.db.models import Count
>>> Fortune.objects.annotate(nb_comments=Count('comments'))
[<Fortune: My first fortune, from NiKo>, <Fortune: Another One, from Dude>, <Fortune: A funny one, from NiKo>]
>>> from django.db import connection
>>> connection.queries.pop()
{'time': '0.000', 'sql': u'SELECT "django_fortunes_fortune"."id", "django_fortunes_fortune"."author", "django_fortunes_fortune"."title", "django_fortunes_fortune"."slug", "django_fortunes_fortune"."content", "django_fortunes_fortune"."pub_date", "django_fortunes_fortune"."votes", COUNT("django_comments"."id") AS "nb_comments" FROM "django_fortunes_fortune" LEFT OUTER JOIN "django_comments" ON ("django_fortunes_fortune"."id" = "django_comments"."object_pk") GROUP BY "django_fortunes_fortune"."id", "django_fortunes_fortune"."author", "django_fortunes_fortune"."title", "django_fortunes_fortune"."slug", "django_fortunes_fortune"."content", "django_fortunes_fortune"."pub_date", "django_fortunes_fortune"."votes" LIMIT 21'}
Below is the properly formatted sql query:
SELECT "django_fortunes_fortune"."id",
"django_fortunes_fortune"."author",
"django_fortunes_fortune"."title",
"django_fortunes_fortune"."slug",
"django_fortunes_fortune"."content",
"django_fortunes_fortune"."pub_date",
"django_fortunes_fortune"."votes",
COUNT("django_comments"."id") AS "nb_comments"
FROM "django_fortunes_fortune"
LEFT OUTER JOIN "django_comments"
ON ("django_fortunes_fortune"."id" = "django_comments"."object_pk")
GROUP BY "django_fortunes_fortune"."id",
"django_fortunes_fortune"."author",
"django_fortunes_fortune"."title",
"django_fortunes_fortune"."slug",
"django_fortunes_fortune"."content",
"django_fortunes_fortune"."pub_date",
"django_fortunes_fortune"."votes"
LIMIT 21
Can you spot the problem? Django won't LEFT JOIN the django_comments table with the content_type data (which contains a reference to the fortune one).
This is the kind of query I'd like to be able to generate using the ORM:
SELECT "django_fortunes_fortune"."id",
"django_fortunes_fortune"."author",
"django_fortunes_fortune"."title",
COUNT("django_comments"."id") AS "nb_comments"
FROM "django_fortunes_fortune"
LEFT OUTER JOIN "django_comments"
ON ("django_fortunes_fortune"."id" = "django_comments"."object_pk")
LEFT OUTER JOIN "django_content_type"
ON ("django_comments"."content_type_id" = "django_content_type"."id")
GROUP BY "django_fortunes_fortune"."id",
"django_fortunes_fortune"."author",
"django_fortunes_fortune"."title",
"django_fortunes_fortune"."slug",
"django_fortunes_fortune"."content",
"django_fortunes_fortune"."pub_date",
"django_fortunes_fortune"."votes"
LIMIT 21
But I don't manage to do it, so help from Django veterans would be much appreciated :)
Hint: I'm using Django 1.2-DEV
Thanks in advance for your help.
