dj_mano 0.2.1

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.

Installation

pip install dj_mano

Usage

In-code

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.

Models

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)

urls.py

from django.conf.urls import patterns
from dj_mano import hook_it_all

hook_it_all()

urlpatterns = patterns('',
    ...
)

Command

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.

./manage.py dj_mano_sync

Licence

This library is licensed under the terms of the WTFPL. Please see the attached LICENSE file.