Materialized Annotations for Django Models
Materialized Annotations for Django Models. Typical use-case is to keep track of the number of comments in a post, or the number of contributions a user has made.
pip install dj_mano
Using dj_mano is pretty straightforward, you just create a field and give it the annotation you want it to hold.
If you want, you can apply some filter to the annotation you’re doing, like to count only positive reviews by example. In this case, you can provide a function that will return the queryset that will be annotated. Beware, the queryset must be “starting” from the object holding the materialized annotation field.
from django.db import models from dj_mano import MaterializedAnnotationIntegerField def swag_model_c(): return ModelA.objects.filter(models_b__models_c__has_swag=True) class ModelA(models.Model): count_b = MaterializedAnnotationIntegerField(models.Count('models_b')) count_c = MaterializedAnnotationIntegerField(models.Count('models_b__models_c')) count_swag = MaterializedAnnotationIntegerField( models.Count('models_b__models_c'), swag_model_c ) class ModelB(models.Model): model_a = models.ForeignKey('ModelA', related_name='models_b') class ModelC(models.Model): model_b = models.ForeignKey('ModelB', related_name='models_c') has_swag = models.BooleanField(default=False)
from django.conf.urls import patterns from dj_mano import hook_it_all hook_it_all() urlpatterns = patterns('', ... )
There is a command that will simply synchronize all fields to their actual value.
Note: if you want to use this command, you have to put dj_mano in your INSTALLED_APPS.
This library is licensed under the terms of the WTFPL. Please see the attached LICENSE file.