Get the first comment per post - mysql

Question

Im using the django comment system and want to fetch only the FIRST comments on posts.
mysql> desc django_comments ;
+-----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| content_type_id | int(11) | NO | MUL | NULL | |
| object_pk | longtext | NO | | NULL | |
| site_id | int(11) | NO | MUL | NULL | |
| user_id | int(11) | YES | MUL | NULL | |
| user_name | varchar(50) | NO | | NULL | |
| user_email | varchar(75) | NO | | NULL | |
| user_url | varchar(200) | NO | | NULL | |
| comment | longtext | NO | | NULL | |
| submit_date | datetime | NO | | NULL | |
| ip_address | char(15) | YES | | NULL | |
| is_public | tinyint(1) | NO | | NULL | |
| is_removed | tinyint(1) | NO | | NULL | |
+-----------------+--------------+------+-----+---------+----------------+
my posts are content_type_id = 48.
I want know the user that left the first comment (min submit_date) of each post (object_pk).
Is there a "django" way to do this?
Or need to use raw SQL?

Answer 1

Use a function like this:
def get_first_comment(post):
from django.contrib.comments.models import Comment
from django.contrib.contenttypes.models import ContentType
ct = ContentType.objects.get_for_model(post)
first_comments = Comment.objects.filter(
content_type=ct,
object_id=post.pk,
).order_by("submit_date")
if first_comments:
return first_comments[0]
return None
It loads the content type for your model instance and then filters comments by the content type and object id sorting them by submit date. Then it takes the first comment if a query is not empty.