django-prefetch-utils 0.1.0

An library of utilities and enhancements for Django's prefetch_related system.

This library currently provides a replacement implementation of prefetch_related_objects which uses an identity map to automatically reduce the number of queries performed when prefetching.

For example, considered the following data model:

class Toy(models.Model):
    dog = models.ForeignKey('dogs.Dog')

class Dog(models.Model):
    name = models.CharField()
    favorite_toy = models.ForeignKey('toys.Toy', null=True)

With this library, we get don’t need to do a database query to perform the prefetch for favorite_toy since that object had already been fetched as part of the prefetching for toy_set:

>>> dog = Dog.objects.prefetch_related('toys', 'favorite_toy')[0]
SELECT * from dogs_dog limit 1;
SELECT * FROM toys_toy where toys_toy.dog_id IN (1);
>>> dog.favorite_toy is dog.toy_set.all()[0]  # no queries done
True

The plan is to increase the scope of the library in future versions to provide additional tools for working with prefetch_related.

• Free software: BSD 3-Clause License

Installation

pip install django-prefetch-utils

Documentation

https://django-prefetch-utils.readthedocs.io/

Changelog

0.1.0 (2019-07-16)

• First release on PyPI.