Connect Django to PostgreSQL in Docker

Django uses SQLite database by default, now we want to switch it to postgreSQL. Firstly, we fetch postgreSQL docker image and start an instance

docker pull postgres
docker run --name my-postgres -v /tmp/my-pgdata:/var/lib/postgresql/data -e POSTGRES_PASSWORD=my-password -p 127.0.0.1:5432:5432 -d postgres

The docker instance name can be whatever you want, here it's named my-postgres for instance, and we mount a volume (e.g /tmp/my-pgdata) to our container, so that the database files are easier to access for other tools or applications on our host system. And remember to forward the default postgreSQL port and use -d to put it to background. Next, we install postgreSQL command line client if you haven't done that yet.

sudo apt-get install postgresql-client

Then, we connect to postgreSQL, either command below should work, postgres is the default database and user name

psql postgresql://postgres:my-password@127.0.0.1:5432/postgres
docker exec -it my-postgres psql postgresql://postgres:my-password@127.0.0.1:5432/postgres

If everything goes as expected, we should be able to connect and list the databases

~ ❯ docker exec -it my-postgres psql postgresql://postgres:my-password@127.0.0.1:5432/postgres
psql (12.3 (Debian 12.3-1.pgdg100+1))
Type "help" for help.

postgres=# \l
                                 List of databases
   Name    |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges
-----------+----------+----------+------------+------------+-----------------------
 postgres  | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
 template0 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
(3 rows)

After it's up and running, we install the postgreSQL adapter psycopg2 to our Django project

pip install psycopg2

Modify settings.py in the project to use Postgres instead

. . .

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': 'my-password',
        'HOST': '127.0.0.1',
        'PORT': '5432'
    }
}

. . .

Now, we are ready to go

python manage.py makemigrations
python manage.py migrate
python manage.py createsuperuser
python manage.py runserver

Let's switch to the database, we can see the default tables are created by Django, cheers!

postgres=# \c postgres
You are now connected to database "postgres" as user "postgres".
postgres=# \dt
                   List of relations
 Schema |            Name            | Type  |  Owner
--------+----------------------------+-------+----------
 public | account_emailaddress       | table | postgres
 public | account_emailconfirmation  | table | postgres
 public | auth_group                 | table | postgres
 public | auth_group_permissions     | table | postgres
 public | auth_permission            | table | postgres
 public | auth_user                  | table | postgres
 public | auth_user_groups           | table | postgres
 public | auth_user_user_permissions | table | postgres
 public | authtoken_token            | table | postgres
 public | django_admin_log           | table | postgres
 public | django_content_type        | table | postgres
 public | django_migrations          | table | postgres
 public | django_session             | table | postgres
 public | django_site                | table | postgres
(18 rows)