[Django]-How can I find the newest match for all names in a Django model?

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4👍

I’m not sure you can do that right away just with the aggregation features of the Django ORM. Anyway, I think this structure is screaming a modeling like this:

class MyModel(Model):
    name = CharField(...)
    some_stuff = ...

class Version(Model):
    number = IntegerField(...)
    my_model = ForeignKey(MyModel, ...)
    other_stuff = ...

So you could do this to get the newest version of every MyModel:

>>> from django.db.models import Max
>>> MyModel.objects.annotate(highest_version = Max('version__number'))
👤Chewie

1👍

I believe you need to group by name, then select on each group. Never used this myself, but this question may offer some insights on how to do it.

Update: it seems I got the code right, but while it should work for your specific case I don’t know yet how to get the other fields in the same query (suppose you wanted not only the version numbers but the other stuff too – this solution won’t work):

from django.db.models import Max
MyModel.objects.values('name').annotate(Max('version'))

# Will return something like:
# [{'name':'a', 'version__max':3}, {'name':'b', 'version__max':2}, ...]

If you’re using Django 1.4 and PostgreSQL, you might be able to do that using the distinct method:

MyModel.objects.order_by('name', '-version').distinct('name')
👤mgibsonbr

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