Question

I have the following models:

class Item(models.Model):
    closed = models.DateTimeField(blank=True, null=True)
    closed_by = models.ForeignKey(User, blank=True, null=True)

class Letter(models.Model):
    item = models.ForeignKey(Item)
    created = models.DateTimeField(default=datetime.now)
    letter_name = models.CharField(max_length=40)
    file_name = models.CharField(max_length=40, blank=True, null=True)
    deleted = models.DateTimeField(blank=True, null=True)
    deleted_by = models.ForeignKey(User, blank=True, null=True)

    def lastVersion(self):
    return self.letterversion_set.order_by('created').latest().created

class LetterVersion(models.Model):
    letter = models.ForeignKey(Letter)
    created = models.DateTimeField(default=datetime.now)
    created_by = models.ForeignKey(User)
    text = models.TextField()

    def letterItem(self):
    return self.letter.item

When a Letter is edited a new Letter Version is created. I am trying to select the last 3 Letters that have been edited recently using LetterVersion.create. I have the following in my views.py:

lettersAll = Letter.objects.filter(item=i_iID,deleted__isnull=True).order_by('-letterversion__created')[:3]

Unfortunately this will get me the last 3 LetterVersions basted on their created date/time even if they are from the same Letter.

letter 1 version 3 [1]
letter 3 version 4 [2]
letter 1 version 2 [3]
letter 1 version 1
letter 2 version 2
letter 2 version 1
letter 3 version 3
letter 3 version 2
letter 3 version 1

Where I want:

letter 1 version 3 [1]
letter 3 version 4 [2]
letter 2 version 2 [3]

Is there anyway I can get a list of the last 3 letters edited?

Answer 1

You can annotate() them with the Max() of letterversion__created, and then order_by() that.

from django.db.models import Max

lettersAll = Letter.objects.filter(
        item=i_iID,
        deleted__isnull=True
    ).annotate(
        last_created_version=Max('letterversion_created')
    ).order_by('-last_created_version')[:3]