CODEWITHSUNDEEP
djangodatetimeaggregate
Charlesliam
Charlesliam

Reputation: 1313

How to filter a query using the max(date) value

I have this model:

class LogBook_audit(models.Model):
    id             = models.AutoField(primary_key=True)
    logbook        = models.ForeignKey(LogBook, verbose_name='Logbook Control No.')
    username       = models.ForeignKey(User, null=True, blank=True,  verbose_name='Username')
    status         = models.CharField(null=False, blank=False, max_length=40, choices=STATUS_TYPE, default=u'CHECKING REQUIREMENTS', verbose_name='Status')
    log_in         = models.DateTimeField(default=lambda:datetime.now(), verbose_name='Work start')

I'm trying to create a queryset to find latest user who log_in for such specific logbook and status.

view.py

undolink(request, pk):
    undo_rec     = LogBook.objects.get(pk=pk)
    latest_user  = LogBook_audit.objects.filter(logbook_id=pk, status=undo_rec.status).aggregate(Max('log_in'))
...

But latest_user is giving me a latest log_in format. I was thinking I can used latest_user.username but failed. Is there a way to find that username? Any guide is really appreciated.

Upvotes: 4

Views: 6801

Answers (2)

dan-klasson
dan-klasson

Reputation: 14180

You can use latest() instead:

latest_log = LogBook_audit.objects.filter(logbook_id=pk, status=undo_rec.status).latest('log_in')

then you can access user through latest_log.user.

Upvotes: 9

Hieu Nguyen
Hieu Nguyen

Reputation: 8623

You want to get a queryset result, so you should use annotate():

latest_user = (LogBook_audit.objects
               .filter(logbook_id=pk, status=undo_rec.status)
               .annotate(max_log_in=Max('log_in')))

Hope it helps.

Upvotes: 1

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