Django DBCache Fields

Keywords:django, database, cache, methods, decorator

Build status coverage Lintly BSD License Supported Python versions Supported Django versions


This library provides a decorator dbcache that caches the result of your Django Model methods in your database.

It adds a regular Field on your Model for each method that you decorate. This means you can use all ORM-functions like aggregation and migrations. You can use existing fields or let dbcache create the field for you.

You can also invalidate the cached value by creating a _dirty_ function or by indicating which other models affect the this cached value. By default, the cached value is only updated when the model is saved.


You can install django_dbcache_fields either via the Python Package Index (PyPI) or from source.

To install using pip:

$ pip install -U django_dbcache_fields


To use this with your project you need to follow these steps:

  1. Install the django_dbcache_fields library:

    $ pip install django_dbcache_fields
  2. Add django_dbcache_fields to INSTALLED_APPS in your Django project’s

        # ...,

    Note that there is no dash in the module name, only underscores.

  3. All done. You can now decorate methods in your Model with @dbcache.


Simple example to show what dbcache does:

from django.db import models
from django_dbcache_fields.decorators import dbcache

class Ingredient(models.Model):
    name = models.CharField(max_length=100)
    price = models.DecimalField(max_digits=4, decimal_places=2)

class Pizza(models.Model):
    name = models.CharField(max_length=100)
    ingredients = models.ManyToManyField(Ingredient)

    @dbcache(models.DecimalField(max_digits=6, decimal_places=2,
             blank=True, null=True), invalidated_by=['myapp.Ingredient'])
    def get_price(self):
        return self.ingredients.aggregate(total=Sum('price'))['total'] or Decimal()

Every call to get_price would normally perform a database query to calculate the total price of all ingredients. However, the dbcache decorator caused a new field to be added to the model: A DecimalField that can store the resulting value of the get_price function, so it doesn’t need to perform the same query over and over again.