Django app that lets you define custom SQL functions
Project description
Django SQL Fun
Django SQLFun allows you to define and manage custom SQL functions in code. When you change the function definitions and call makemigrations
, it will generate migrations for any functions that have been added, removed, or changed. These function classes can also be used in Django querysets since the SqlFun
class inherits from django.db.models.expressions.Func
.
Note: I'm still developing this so there may be some rough edges. Breaking changes may happen.
Installation
- Install using your favorite python package manager, eg.
pip install django-sqlfun
. - Add
sqlfun
toINSTALLED_APPS
in your django settings - Run
manage.py migrate
. This will set up any tables required bysqlfun
to keep track of your custom funcitons
Use
- Define a custom function in a module that gets imported on project load (eg.
models.py
). See below for example, or thetest_project
. - Run
manage.py makemigrations
- Run
manage.py migrate
Example
Define a custom function in your models.py
:
# models.py
from sqlfun import SqlFun
from django.db.models import IntegerField
class BadSum(SqlFun):
"""Almost returns the sum of two numbers."""
app_label = 'test_project' # [optional] if omitted, sqlfun will atempt to auto-resolve it
sql = """
CREATE OR REPLACE FUNCTION bad_sum(
first integer,
second integer
) RETURNS integer as $$
SELECT first + second + 1;
$$
LANGUAGE sql
stable;
"""
output_field = IntegerField()
Then run manage.py makemigrations
and manage.py migrate
and you should be good to go. You can use it in SQL: SELECT bad_sum(2, 2)
, or in a Python queryset like so: MyModel.objects.annotate(foo=BadSum(Value(2), Value(2)))
.
Notes
- SQL functions are normalized, so changes in white-space should not result in changes being detected
- the
--dry-run
and--name
options ofmakemigrations
are respected
Development
These instructions assume a recent Ubuntu/Debian environment.
- Clone the repository
- If needed, install
python3-venv
andpython3-pip
packages - Create a virtual environment
python3 -m venv .venv
- Install
libpq-dev
package sincepsycopg2
depends on it. - Install
pdm
:pip3 install --user pdm
- Install dev dependencies with
pdm install --dev
Testing also requires a recent install of docker which is used to spin up a test postgres instance.
Credits
This project is inspired by two great projects: django-pgtrigger
and django-pgviews
.
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