MongoDB backend for Django

This backend is in currently in development and is not advised for Production workflows. Backwards incompatible changes may be made without notice. We welcome your feedback as we continue to explore and build. The best way to share this is via our MongoDB Community Forum

Install and usage

The development version of this package supports Django 5.0.x. To install it:

pip install git+https://github.com/mongodb-labs/django-mongodb

Specifying the default primary key field

In your Django settings, you must specify that all models should use ObjectIdAutoField.

You can create a new project that's configured based on these steps using a project template:

$ django-admin startproject mysite --template https://github.com/mongodb-labs/django-mongodb-project/archive/refs/heads/5.0.x.zip

(where "5.0" matches the version of Django that you're using.)

This template includes the following line in settings.py:

DEFAULT_AUTO_FIELD = "django_mongodb.fields.ObjectIdAutoField"

But this setting won't override any apps that have an AppConfig that specifies default_auto_field. For those apps, you'll need to create a custom AppConfig.

For example, the project template includes <project_name>/apps.py:

from django.contrib.admin.apps import AdminConfig
from django.contrib.auth.apps import AuthConfig
from django.contrib.contenttypes.apps import ContentTypesConfig


class MongoAdminConfig(AdminConfig):
    default_auto_field = "django_mongodb.fields.ObjectIdAutoField"


class MongoAuthConfig(AuthConfig):
    default_auto_field = "django_mongodb.fields.ObjectIdAutoField"


class MongoContentTypesConfig(ContentTypesConfig):
    default_auto_field = "django_mongodb.fields.ObjectIdAutoField"

Each app reference in the INSTALLED_APPS setting must point to the corresponding AppConfig. For example, instead of 'django.contrib.admin', the template uses '<project_name>.apps.MongoAdminConfig'.

Configuring migrations

Because all models must use ObjectIdAutoField, each third-party and contrib app you use needs to have its own migrations specific to MongoDB.

For example, settings.py in the project template specifies:

MIGRATION_MODULES = {
    "admin": "mongo_migrations.admin",
    "auth": "mongo_migrations.auth",
    "contenttypes": "mongo_migrations.contenttypes",
}

The project template includes these migrations, but you can generate them if you're setting things up manually or if you need to create migrations for third-party apps. For example:

$ python manage.py makemigrations admin auth contenttypes
Migrations for 'admin':
  mongo_migrations/admin/0001_initial.py
    - Create model LogEntry
...

Creating Django applications

Whenever you run python manage.py startapp, you must remove the line:

default_auto_field = 'django.db.models.BigAutoField'

from the new application's apps.py file (or change it to reference "django_mongodb.fields.ObjectIdAutoField").

Alternatively, you can use the following startapp template which includes this change:

$ python manage.py startapp myapp --template https://github.com/mongodb-labs/django-mongodb-app/archive/refs/heads/5.0.x.zip

(where "5.0" matches the version of Django that you're using.)

Configuring the DATABASES setting

After you've set up a project, configure Django's DATABASES setting similar to this:

DATABASES = {
    "default": {
        "ENGINE": "django_mongodb",
        "HOST": "mongodb+srv://cluster0.example.mongodb.net",
        "NAME": "my_database",
        "USER": "my_user",
        "PASSWORD": "my_password",
        "PORT": 27017,
        "OPTIONS": {
            # Example:
            "retryWrites": "true",
            "w": "majority",
            "tls": "false",
        },
    },
}

For a localhost configuration, you can omit HOST or specify "HOST": "localhost".

HOST only needs a scheme prefix for SRV connections (mongodb+srv://). A mongodb:// prefix is never required.

OPTIONS is an optional dictionary of parameters that will be passed to MongoClient.

USER, PASSWORD, and PORT (if 27017) may also be optional.

For a replica set or sharded cluster where you have multiple hosts, include all of them in HOST, e.g. "mongodb://mongos0.example.com:27017,mongos1.example.com:27017".

Alternatively, if you prefer to simply paste in a MongoDB URI rather than parse it into the format above, you can use:

import django_mongodb

MONGODB_URI = "mongodb+srv://my_user:my_password@cluster0.example.mongodb.net/myDatabase?retryWrites=true&w=majority&tls=false"
DATABASES["default"] = django_mongodb.parse_uri(MONGODB_URI)

This constructs a DATABASES setting equivalent to the first example.

django_mongodb.parse_uri(uri, conn_max_age=0, test=None)

parse_uri() provides a few options to customize the resulting DATABASES setting, but for maximum flexibility, construct DATABASES manually as described above.

• Use conn_max_age to configure persistent database connections.
• Use test to provide a dictionary of settings for test databases.

Congratulations, your project is ready to go!

Notes on Django QuerySets

• QuerySet.explain() supports the comment and verbosity options.

  Example: QuerySet.explain(comment="...", verbosity="...")

  Valid values for verbosity are "queryPlanner" (default), "executionStats", and "allPlansExecution".

Known issues and limitations

• The following QuerySet methods aren't supported:

  • bulk_update()
  • dates()
  • datetimes()
  • distinct()
  • extra()
  • prefetch_related()

• QuerySet.delete() and update() do not support queries that span multiple collections.

• DateTimeField doesn't support microsecond precision, and correspondingly, DurationField stores milliseconds rather than microseconds.

• The following database functions aren't supported:

  • Chr
  • ExtractQuarter
  • MD5
  • Now
  • Ord
  • Pad
  • Repeat
  • Reverse
  • Right
  • SHA1, SHA224, SHA256, SHA384, SHA512
  • Sign

• The tzinfo parameter of the Trunc database functions doesn't work properly because MongoDB converts the result back to UTC.

• When querying JSONField:

  • There is no way to distinguish between a JSON "null" (represented by Value(None, JSONField())) and a SQL null (queried using the isnull lookup). Both of these queries return both of these nulls.
  • Some queries with Q objects, e.g. Q(value__foo="bar"), don't work properly, particularly with QuerySet.exclude().
  • Filtering for a None key, e.g. QuerySet.filter(value__j=None) incorrectly returns objects where the key doesn't exist.
  • You can study the skipped tests in DatabaseFeatures.django_test_skips for more details on known issues.

• Due to the lack of ability to introspect MongoDB collection schema, migrate --fake-initial isn't supported.

Troubleshooting

Debug logging

To troubleshoot MongoDB connectivity issues, you can enable PyMongo's logging using Django's LOGGING setting.

This is a minimal LOGGING setting that enables PyMongo's DEBUG logging:

LOGGING = {
    "version": 1,
    "disable_existing_loggers": False,
    "handlers": {
        "console": {
            "class": "logging.StreamHandler",
        },
    },
    "loggers": {
        "pymongo": {
            "handlers": ["console"],
            "level": "DEBUG",
        },
    },
}