Django model for sparse data - django

Question

I am developing a django app that contains a number of forms which will be used to enter clinical data on some cancer tissue samples (10-20 fields per form, mostly CharField, FloatField and some multiple choice text dropdowns).
My challenge is that I need a form that can display different fields based on a diagnosis, for 150+ diagnoses. I can programmatically read the list of diagnoses, the fields required for each diagnosis and corresponding field types. Also, the set of all unique fields across all diagnoses is large (much larger than the number of fields needed for any specific diagnosis).
e.g.
disease_specific_fields field_type
diagnosis
B-lymphoblastic leukemia/lymphoma NOS EBV-positive Pull down: Yes/No
B-lymphoblastic leukemia/lymphoma with recurrent genetic abnormalities(TCF3-PBX1) EBV-positive Pull down: Yes/No
Monoclonal B lymphocytosis(CLL/SLL spectrum) EBV-positive Pull down: Yes/No
Peripheral T cell lymphoma NOS EBV-positive Pull down: Yes/No
AML with recurrent cytogenetic abnormalities(t(6;9) DEK-NUP214) EBV-positive Pull down: Yes/No
So far, I thought of the following approaches:
Create a single huge model that will contain mostly sparse data, and handle irrelevant data using django forms. CONS: inefficient storage and a lot of overhead code tied to forms.
Create a model for each diagnosis. CONS: complicates migrations and maintenance, I think.
Create one small model for all diagnoses that contains several 'generic' fields of each type ('CharField', 'FloatField', etc), and render respective field names dynamically in forms / views.
I am looking for any constructive suggestions on how to implement a model/models capturing the above data. Efficiency and storage are secondary concerns, mostly I want a clean and intuitive solution. Any answers tailored for django will be especially helpful.

Answer 1

A few options I'd consider-
Use Django-Polymorphic to create inheritance-based model types
Django-Polymorphic allows you to use inheritance for differentiating between types of models.
from polymorphic.models import PolymorphicModel
class Animal(PolymorphicModel):
kingdom = models.CharField(default="Animalia")
class Lizard(Animal):
class = models.CharField(default="Reptilia")
class Iguana(Lizard):
favorite_tree = models.Charfield()
While polymorphic uses a single db table for any model in an inheritance scheme, types are stored. As such, if you know the specific fields you want to capture hard-code it. Plus, you can filter by level (So, you could run a query on all Animal instances or all Iguana instances in the example above). There's no relations created by a polymorphic model, so performance is extremely good.
Use Django-Mutant if dynamic field creation is needed
Django-Mutant allows for dynamic creation of fields per model, allowing you top define data as needed on the fly. However, intermediary tables are required to do this. You gain a lot of flexibility while losing performance.
Use the postgres-specific JsonField to store data
Django 1.9 introduced native support for field type JsonField, allowing you to write Json structures to a db field as well as query them relatively quickly. You get amazing flexibility with decent performance but may struggle in providing user friendly forms to create, update, and verify the data. However, it has been done in many projects and there are libraries out there to assist with it.
from django.contrib.postgres.fields import JSONField
from django.db import models
class SomeModel(models.Model):
attributes = JsonField()
>>> some_attributes = {'color':'red', 'cell_count':150, 'enzymes':['xyzyss','xyxzxxyx']}
>>> a = SomeModel.objects.create(attributes=some_attributes)
>>> SomeModel.objects.filter(attributes__color='red')
(<<< will return a queryset with instance 'a' in it >>>)