Dynamic Models with Django

Dynamic Models
in Django
Juergen Schackmann
j.schackmann@reliatec.de

© Juergen Schackmann 2013 2/28
Me
▸ Python & Django since 4 years
▸ reliatec.de since 3 months
▸ Django Web Applications
▸ Focus: EDC systems for clinical studies & Telemonitoring

Objective
▸ Why do do we care about Django Dynamic Models?
▸ Why do we have to talk about them?
▸ What should we do about them?

Models in a Django project
Phase1:
Code Development
Models and model
attributes are defined by
implementing those with
Python code
Phase 2:
Deployment
Underlying database tables
and columns are created by
running “syncdb” command
Phase 3:
Runtime
Models / DB Tables are
populated with content as
part of the user
interactions

Problem?
There is no way to adapt the Django Models at runtime based on
user interactions
▸ Django Models are defined and implemented during
development phase
▸ Django Models are expected to be static after deployment
▸ Django DB Backends only fully support SQL databases, i.e. a
schema is required
▸ DB specific solutions limit adoption rate of any reusable App

Custom Content Types for a CMS*
* system: dotCms (Java); source: http://dotcms.com/

Customized Products for an Ecommerce Shop*
* system: Magento (PHP); source: averybrandandprint.co.uk

Clinical Research Forms*
* system: OpenClinica (Java); source: openclinica.com

Problem? Which Problem?
▸ Models / Content Types are domain or site specific
▸ Neither realistic nor efficient to implement all thinkable content
types into a software product
▸ Configuration by subject-matter experts is better, than code
customization by developers
▸ Dynamic Models reduce the number of deployment cycles

As a User, I ...
▸ want to maintain my dynamic models easily without
understanding any Django Model details
▸ want extend existing (static) models without thinking about
static and dynamic parts
▸ do not want to think about performance, when creating my
custom fields
▸ I want to be able to query/search for certain information
seamlessly over static and dynamic models

As a developer, I ...
▸ want my dynamic models to be integrated with Django Standard
Tools (admin, migrations, reversion) out of the box
▸ want to apply the same API that I use for the static models
▸ do not want to use or be limited to specific databases, but use
the standard Django backends
▸ want to have a customizable front-end for my users to manage
the dynamic models

Evaluation Criteria
▸ Performance
▸ “Querybility”
▸ Django Standard Tools Integration (Admin, Cache, ...)
▸ Supported Backend
▸ Complexity/ Maintainability

Entity Attribute Value (EAV)
Transform your table columns into table rows
Attribute 1 Attribute 2 Attribute n
Table
Attribute
Name
Attribute
Value
Attribute
TableTable has1 n

EAV Django Apps
▸ bitbucket.org/neithere/eav-django/
▸ github.com/mvpdev/django-eav

Serialized Dictionary
Transform your table columns into pickeld or jsoned dictionaries
Attribute 1 Attribute 2 Attribute n
Table
Dictionary
String
Attributes
{“attribute1”:”a”, “attribute2”: 5, “attribute3”:[1,2] }

Serialized Dictionary Django Apps
Fields
▸ bitbucket.org/schinckel/django-jsonfield/
▸ github.com/bradjasper/django-jsonfield
▸ github.com/derek-schaefer/django-json-field
▸ github.com/shrubberysoft/django-picklefield
App
▸ github.com/dobarkod/django-dynamic-model

Runtime Schema Updates
Update Django models and database schema at runtime using
▸ syncdb functionality
▸ South functionality
▸ eventually: Andrew Godwin's “Schema Migrations for Django”

Runtime Schema Update Django Apps
Update Django models and database schema at runtime using
▸ Syncdb
▸ bitbucket.org/mhall119/dynamo/overview
▸ South
▸ github.com/willhardy/dynamic-models
▸ github.com/willhardy/django-dymo
▸ bitbucket.org/schacki/django-dynamo
▸ github.com/charettes/django-mutant
▸ Schema Migrations
▸ github.com/charettes/django-mutant

Database specific solutions
Hstore
▸ github.com/jordanm/django-hstore
▸ postgresql.org/docs/9.0/static/hstore.html
No SQL
▸ github.com/django-nonrel
▸ github.com/pydanny/django-mongonaut

Summary
EAV Serialization Schema Updates
Performance   
Querybility   
Django Standard
Tools
 / 
Supported
Backend
  
Complexity/
Maintainability
  

Schema Update most powerful, but ...
▸ Name clashes between developer models and dynamic models
(especially with schema migrations)
▸ Multiple Users updating the same model (possibly even
conflicting)
▸ Orphan database elements
▸ Dynamic Model loading at startup
▸ How to find/inject dynamic models into views and templates

Components of a
Dynamic Model App

Must have components of a Dynamic Model
Application
▸ Meta Model Front End to let users maintain their meta models
▸ Meta Model Representation to store the meta model information
▸ Meta Model Analyzer to detect changes that require some further
actions (for schema, admin or model)
▸ Schema Sync Manager to update and sync the database schema
▸ Admin Sync Manager to update and sync the Django admin
▸ Model/Cache Sync Manager to update and sync the Django models
and model cache

More resources on dynamic models
▸ code.djangoproject.com/wiki/DynamicModels
▸ djangopackages.com/grids/g/forms/
▸ stackoverflow.com/questions/7933596/django-dynamic-model-
fields/7934577

Thank you very much!
Questions please?

Dynamic Models with Django

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (15)

Semelhante a Dynamic Models with Django

Semelhante a Dynamic Models with Django (20)

Último

Último (20)

Dynamic Models with Django