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googleapis / python-spanner-django

Cloud Spanner database backend for Django
BSD 3-Clause "New" or "Revised" License
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Cloud Spanner support for Django

|GA| |pypi| |versions|

Cloud Spanner_ is the world's first fully managed relational database service to offer both strong consistency and horizontal scalability for mission-critical online transaction processing (OLTP) applications. With Cloud Spanner you enjoy all the traditional benefits of a relational database; but unlike any other relational database service, Cloud Spanner scales horizontally to hundreds or thousands of servers to handle the biggest transactional workloads.

.. |GA| image:: https://img.shields.io/badge/support-GA-gold.svg :target: https://github.com/googleapis/google-cloud-python/blob/main/README.rst#general-availability .. |pypi| image:: https://img.shields.io/pypi/v/django-google-spanner.svg :target: https://pypi.org/project/django-google-spanner/ .. |versions| image:: https://img.shields.io/pypi/pyversions/django-google-spanner.svg :target: https://pypi.org/project/django-google-spanner/ .. _Cloud Spanner: https://cloud.google.com/spanner/ .. _Client Library Documentation: https://googleapis.dev/python/django-google-spanner/latest/index.html .. _Product Documentation: https://cloud.google.com/spanner/docs

Quick Start

In order to use this library, you first need to go through the following steps:

  1. Select or create a Cloud Platform project._
  2. Enable billing for your project._
  3. Enable the Google Cloud Spanner API._
  4. Setup Authentication._

.. _Select or create a Cloud Platform project.: https://console.cloud.google.com/project .. _Enable billing for your project.: https://cloud.google.com/billing/docs/how-to/modify-project#enable_billing_for_a_project .. _Enable the Google Cloud Spanner API.: https://cloud.google.com/spanner .. _Setup Authentication.: https://googleapis.dev/python/google-api-core/latest/auth.html

This package provides a 3rd-party database backend <https://docs.djangoproject.com/en/2.2/ref/databases/#using-a-3rd-party-database-backend> for using Cloud Spanner <https://cloud.google.com/spanner> with the Django ORM <https://docs.djangoproject.com/en/2.2/topics/db/>. It uses the Cloud Spanner Python client library <https://github.com/googleapis/python-spanner> under the hood.

Installation

Install this library in a virtualenv using pip. virtualenv is a tool to create isolated Python and Django environments. The basic problem it addresses is one of dependencies and versions, and indirectly permissions.

With virtualenv_, it's possible to install this library without needing system install permissions, and without clashing with the installed system dependencies.

.. _virtualenv: https://virtualenv.pypa.io/en/latest/

Supported versions


The library supports `Django 2.2
<https://docs.djangoproject.com/en/2.2/>`_, and `Django 3.2
<https://docs.djangoproject.com/en/3.2/>`_.
Both versions are long-term support (LTS) releases for the
`Django project<https://www.djangoproject.com/download/#supported-versions>_`.
The minimum required Python version is 3.6.

.. code:: shell

    pip3 install django==3.2

Installing the package

To install from PyPI:

.. code:: shell

pip3 install django-google-spanner

To install from source:

.. code:: shell

git clone git@github.com:googleapis/python-spanner-django.git
cd python-spanner-django
pip3 install -e .

Creating a Cloud Spanner instance and database


If you don't already have a Cloud Spanner database, or want to start from
scratch for a new Django application, you can `create a new instance
<https://cloud.google.com/spanner/docs/getting-started/python#create_an_instance>`__
and `database
<https://cloud.google.com/spanner/docs/getting-started/python#create_a_database>`__
using the Google Cloud SDK:

.. code:: shell

    gcloud spanner instances create $INSTANCE --config=regional-us-central1 --description="New Django Instance" --nodes=1
    gcloud spanner databases create $DB --instance $INSTANCE

Configuring ``settings.py``

This package provides a Django application named django_spanner. To use the Cloud Spanner database backend, the application needs to installed and configured:

Transaction support in autocommit mode


Django version 4.2 and higher by default supports transactions in autocommit mode.
A transaction is automatically started if you define an
[atomic block](https://docs.djangoproject.com/en/4.2/topics/db/transactions/#controlling-transactions-explicitly).

Django version 3.2 and earlier did not support transactions in autocommit mode with Spanner.
You can enable transactions in autocommit mode with Spanner with the
`ALLOW_TRANSACTIONS_IN_AUTO_COMMIT` configuration option.

- To enable transactions in autocommit mode in V3.2, set the flag `ALLOW_TRANSACTIONS_IN_AUTO_COMMIT` to True in your settings.py file.
- To disable transactions in autocommit mode in V4.2, set the flag `ALLOW_TRANSACTIONS_IN_AUTO_COMMIT` to False in your settings.py file.

Set credentials and project environment variables

You'll need to download a service account JSON key file and point to it using an environment variable:

.. code:: shell

export GOOGLE_APPLICATION_CREDENTIALS=/path/to/keyfile.json
export GOOGLE_CLOUD_PROJECT=gcloud_project

Apply the migrations


Please run:

.. code:: shell

    $ python3 manage.py migrate

That'll take a while to run. After this you should be able to see the tables and indexes created in your Cloud Spanner console.

Create a Django admin user

First you’ll need to create a user who can login to the admin site. Run the following command:

.. code:: shell

$ python3 manage.py createsuperuser

which will then produce a prompt which will allow you to create your super user

.. code:: shell

Username: admin
Email address: admin@example.com
Password: **********
Password (again): **********
Superuser created successfully.

Login as admin

Now, run the server

.. code:: shell

    python3 manage.py runserver

Then visit http://127.0.0.1:8000/admin/

Create and register your first model

Please follow the guides in https://docs.djangoproject.com/en/2.2/intro/tutorial02/#creating-models to create and register the model to the Django’s automatically-generated admin site.

How it works

Overall design


.. figure:: https://raw.githubusercontent.com/googleapis/python-spanner-django/main/assets/overview.png
   :alt: "Overall Design"

Internals

.. figure:: https://raw.githubusercontent.com/googleapis/python-spanner-django/main/assets/internals.png :alt: "Internals"

Executing a query


Here is an example of how to add a row for Model Author, save it and later query it using Django

.. code:: shell

    >>> author_kent = Author( first_name="Arthur", last_name="Kent", rating=Decimal("4.1"),)
    >>> author_kent.save()
    >>> qs1 = Author.objects.all().values("first_name", "last_name")

How to contribute

Contributions to this library are always welcome and highly encouraged.

See CONTRIBUTING <https://github.com/googleapis/python-spanner-django/blob/main/CONTRIBUTING.md>_ for more information on how to get started.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. See the Code of Conduct <https://github.com/googleapis/python-spanner-django/blob/main/CODE_OF_CONDUCT.md>_ for more information.

Limitations



Spanner has certain limitations of its own. The full set of limitations is documented
`here <https://cloud.google.com/spanner/quotas#schema_limits>`__.
It is recommended that you go through that list.

Django spanner has a set of limitations as well, which you can find
`here <https://github.com/googleapis/python-spanner-django/blob/main/docs/limitations.rst>`__.

Features from spanner that are not supported in Django-spanner are listed 
`here <https://github.com/googleapis/python-spanner-django/blob/main/docs/limitations-spanner.rst>`__.