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Aggregate-if adds conditional aggregates to Django.
Conditional aggregates can help you reduce the ammount of queries to obtain aggregated information, like statistics for example.
Imagine you have a model Offer
like this one:
.. code-block:: python
class Offer(models.Model):
sponsor = models.ForeignKey(User)
price = models.DecimalField(max_digits=9, decimal_places=2)
status = models.CharField(max_length=30)
expire_at = models.DateField(null=True, blank=True)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
OPEN = "OPEN"
REVOKED = "REVOKED"
PAID = "PAID"
Let's say you want to know:
To get these informations, you could query:
.. code-block:: python
from django.db.models import Count, Sum
Offer.objects.count()
Offer.objects.filter(status=Offer.OPEN).aggregate(Count('pk'))
Offer.objects.filter(status=Offer.REVOKED).aggregate(Count('pk'))
Offer.objects.filter(status=Offer.PAID).aggregate(Count('pk'))
Offer.objects.aggregate(Sum('price'))
Offer.objects.filter(status=Offer.OPEN).aggregate(Sum('price'))
Offer.objects.filter(status=Offer.REVOKED).aggregate(Sum('price'))
Offer.objects.filter(status=Offer.PAID).aggregate(Sum('price'))
In this case, 8 queries were needed to retrieve the desired information.
With conditional aggregates you can get it all with only 1 query:
.. code-block:: python
from django.db.models import Q
from aggregate_if import Count, Sum
Offer.objects.aggregate(
pk__count=Count('pk'),
pk__open__count=Count('pk', only=Q(status=Offer.OPEN)),
pk__revoked__count=Count('pk', only=Q(status=Offer.REVOKED)),
pk__paid__count=Count('pk', only=Q(status=Offer.PAID)),
pk__sum=Sum('price'),
pk__open__sum=Sum('price', only=Q(status=Offer.OPEN)),
pk__revoked__sum=Sum('price'), only=Q(status=Offer.REVOKED)),
pk__paid__sum=Sum('price'), only=Q(status=Offer.PAID))
)
Aggregate-if works with Django 1.4, 1.5, 1.6 and 1.7.
To install it, simply:
.. code-block:: bash
$ pip install django-aggregate-if
There is a 5 years old ticket 11305
_ that will (hopefully) implement this feature into
Django 1.8.
Using Django 1.6, I still wanted to avoid creating custom queries for very simple conditional aggregations. So I've cherry picked those ideas and others from the internet and built this library.
This library uses the same API and tests proposed on ticket 11305
_, so when the
new feature is available you can easily replace django-aggregate-if
.
Conditions involving joins with aliases are not supported yet. If you want to
help adding this feature, you're welcome to check the first issue
_.
Henrique Bastos <http://github.com/henriquebastos>
_Iuri de Silvio <https://github.com/iurisilvio>
_Hampus Stjernhav <https://github.com/champ>
_Bradley Martsberger <https://github.com/martsberger>
_Markus Bertheau <https://github.com/mbertheau>
_end0 <https://github.com/end0>
_Scott Sexton <https://github.com/scottsexton>
_Mauler <https://github.com/mauler>
_trbs <https://github.com/trbs>
_0.5
0.4
only
parameter now freely supports joins independent of the main query.0.3.1
0.2
0.1
The MIT License.
.. _ticket 11305: https://code.djangoproject.com/ticket/11305 .. _first issue: https://github.com/henriquebastos/django-aggregate-if/issues/1