How to Implement Dynamic Django Model Fields for Multi-Tenant Applications?

Dynamic Django Model Fields for Multi-Tenant Applications

When designing multi-tenant applications, it's often desirable to provide users with the ability to define their own custom data fields. However, creating and managing dynamic fields in a relational database can be complex. This article explores various approaches for tackling this challenge in Django.

Django-eav

The django-eav package, now maintained in several thriving forks, implements the Entity-Attribute-Value pattern. By storing dynamic attributes in a few simple Django models, this solution provides:

• Database-agnostic storage
• Seamless integration with Django admin
• Powerful capabilities for managing dynamic fields

However, it suffers from potential performance and maintenance issues.

PostgreSQL Storage Backends

PostgreSQL offers several data types for storing dynamic data, including:

• HStoreField: Offers key-value pairs, but limited to string values and potentially slower performance with high item counts.
• JSONField: Supports a wider range of data types and generally performs better than HStoreField, including nested data structures.
• JSONBField: Built-in in Django 1.9, offers even better performance and data compression than JSONField.

These fields allow for indexed queries and can be used as follows:

class Something(models.Model):
    data = JSONField(db_index=True)  # JSON or JSONB

something = Something.objects.create(data={'a': 1, 'b': 2})
Something.objects.filter(data__a=1)

Django MongoDB

Alternatively, Django MongoDB provides a fully dynamic modeling solution, enabling embedded documents and lists of models.

from djangotoolbox.fields import DictField

class Image(models.Model):
    exif = DictField()

image = Image.objects.create(exif=get_exif_data(...))

Django-mutant

Django-mutant offers dynamic Foreign Key and many-to-many fields, inspired by Michael Hall's approach. It leverages Django South hooks to dynamically alter database schemas at runtime, allowing for fully dynamic Django apps, models, and fields.

from dynamo import models

test = models.DynamicModel.objects.create(name='Test')
foo = models.DynamicModelField.objects.create(model=test, name='foo')

It's important to note the potential stability risks and locking considerations when using these dynamic approaches. However, they provide powerful options for managing dynamic data in Django.

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