django-optimistic-admin-pg

This app provides a couple of mixins to implement optimistic concurrency in the Django admin leveraging PostgreSQL specific features.

PostgreSQL implements an MVCC concurrency model, that means that rows are duplicated on update. PostgreSQL stores an id on each row to store the transaction identifier called xmin.

This application provides mixins for Django ModelForm and ModelAdmin using the xmin value to inhibit the saving of data via the Django admin if it has been updated in the meantime.

Notes on safety

Please note that this application does not remove completely the races between updates via the admin interfaces but it narrows them by a lot.

Similar Projects

django-concurrency implements the same pattern with batteries included in a database-independent way.

Requirements

The app is tested on Python 3.8+ with Django 3.2 and 4.0.

Setup

python -m pip install django-optimistic-admin-pg

How to use

This application provides a couple of mixins: one for ModelAdmin instances and one for ModelForm instances.

First a ModelForm inheriting from OptimisticAdminModelFormMixin should be used as form the ModelAdmin. A field called row_version should be added to this form in order to send the row version read from the database. Assuming you have forms in forms.py:

from django import forms
from optimisticadmin.mixins import OptimisticAdminModelFormMixin

class MyModelForm(OptimisticAdminModelFormMixin, forms.ModelForm):
    row_version = forms.IntegerField(required=False, widget=forms.HiddenInput())

Then in admin.py your ModelAdmin need to inherit from OptimisticAdminMixin and use the form implemented before:

from django.contrib import admin
from optimisticadmin.mixins import OptimisticAdminMixin
from .forms import MyModelForm

@admin.register(MyModel)
class MyModelAdmin(OptimisticAdminMixin, admin.ModelAdmin):
    form = MyModelForm