Annotate querying, pk - django

Question

How should I query when I use pk with annotate?
I need to redirect to user profile when a guest click in link.
Models
class Posty(models.Model):
title = models.CharField(max_length=250, blank=False, null=False, unique=True)
sub_title = models.SlugField(max_length=250, blank=False, null=False, unique=True)
content = models.TextField(max_length=250, blank=False, null=False)
image = models.ImageField(default="avatar.png",upload_to="images", validators=[FileExtensionValidator(['png','jpg','jpeg'])])
author = models.ForeignKey(Profil, on_delete=models.CASCADE)
updated = models.DateTimeField(auto_now=True)
published = models.DateTimeField(auto_now_add=True)
T_or_F = models.BooleanField(default=False)
likes = models.ManyToManyField(Profil, related_name='liked')
unlikes = models.ManyToManyField(Profil, related_name='unlikes')
created_tags = models.ForeignKey('Tags', blank=True, null=True, related_name='tagi', on_delete=models.CASCADE)
class CommentPost(models.Model):
user = models.ForeignKey(Profil, on_delete=models.CASCADE)
post = models.ForeignKey(Posty, on_delete=models.CASCADE, related_name="comments")
content1 = models.TextField(max_length=250, blank=False, null=False)
date_posted = models.DateTimeField(default=timezone.now)
date_updated = models.DateTimeField(auto_now=True)
def __str__(self):
return str(self.content1)
class Profil(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
age = models.PositiveIntegerField(blank=True, null=True)
country = models.CharField(max_length=50)
user = models.OneToOneField(Account, on_delete=models.CASCADE)
avatar = models.ImageField(default="avatar.png", upload_to="images",validators=[FileExtensionValidator(['png', 'jpg', 'jpeg'])])
slug = models.SlugField(blank=True)
gender = models.CharField(max_length=6, choices=GENDER)
friends = models.ManyToManyField(Account, blank=True, related_name="Friends")
social_facebook = models.CharField(max_length=250, null=True, blank=True)
social_instagram = models.CharField(max_length=250, null=True, blank=True)
social_twitter = models.CharField(max_length=250, null=True, blank=True)
social_youtube = models.CharField(max_length=250, null=True, blank=True)
social_linkedin = models.CharField(max_length=250, null=True, blank=True)
updated = models.DateTimeField(auto_now=True)
created = models.DateTimeField(auto_now_add=True)
Views
if tag == None:
my_tag = Posty.objects.annotate(
latest_comment = Subquery(CommentPost.objects.filter(post=OuterRef('id')).values('content1').order_by('-date_posted')[:1]),
my_author=Subquery(CommentPost.objects.filter(post=OuterRef('id')).values('user__user__username').order_by('-date_posted')[:1]),
)
I got a correct username, but I can't get a correct redirect:

Answer 1

Unfortunately, you need to annotate the CommentPost's id information as well with the queryset just like you added the username information. That will end up being a lot of subquery added to the original queryset. Rather I would suggest to use prefetch related to preload the CommentPost information with the original queryset (for reducing DB hits) and directly access that information from template. For example:
# view
my_tag = Posty.objects.prefetch_related('commentpost_set')
# template
{% for post in my_tag %}
<span> {{post.commentpost_set.last.content1}}<span>
<span> {{post.commentpost_set.last.user.username}}<span>
{% endfor %}
Also, last is a queryset function which returns the last object of a given queryset. I can access the CommentPost queryset from a Posty object by reverse querying.