Contenu connexe Similaire à Dynamic Models with Django (20) 2. © 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
3. © Juergen Schackmann 2013 3/28
Objective
▸ Why do do we care about Django Dynamic Models?
▸ Why do we have to talk about them?
▸ What should we do about them?
5. © Juergen Schackmann 2013 5/28
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
6. © Juergen Schackmann 2013 6/28
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
8. © Juergen Schackmann 2013 8/28
Custom Content Types for a CMS*
* system: dotCms (Java); source: http://dotcms.com/
9. © Juergen Schackmann 2013 9/28
Customized Products for an Ecommerce Shop*
* system: Magento (PHP); source: averybrandandprint.co.uk
10. © Juergen Schackmann 2013 10/28
Clinical Research Forms*
* system: OpenClinica (Java); source: openclinica.com
11. © Juergen Schackmann 2013 11/28
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
13. © Juergen Schackmann 2013 13/28
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
14. © Juergen Schackmann 2013 14/28
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
15. © Juergen Schackmann 2013 15/28
Evaluation Criteria
▸ Performance
▸ “Querybility”
▸ Django Standard Tools Integration (Admin, Cache, ...)
▸ Supported Backend
▸ Complexity/ Maintainability
16. © Juergen Schackmann 2013 16/28
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
17. © Juergen Schackmann 2013 17/28
EAV Django Apps
▸ bitbucket.org/neithere/eav-django/
▸ github.com/mvpdev/django-eav
18. © Juergen Schackmann 2013 18/28
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] }
19. © Juergen Schackmann 2013 19/28
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
20. © Juergen Schackmann 2013 20/28
Runtime Schema Updates
Update Django models and database schema at runtime using
▸ syncdb functionality
▸ South functionality
▸ eventually: Andrew Godwin's “Schema Migrations for Django”
21. © Juergen Schackmann 2013 21/28
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
22. © Juergen Schackmann 2013 22/28
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
23. © Juergen Schackmann 2013 23/28
Summary
EAV Serialization Schema Updates
Performance
Querybility
Django Standard
Tools
/
Supported
Backend
Complexity/
Maintainability
24. © Juergen Schackmann 2013 24/28
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
26. © Juergen Schackmann 2013 26/28
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
27. © Juergen Schackmann 2013 27/28
More resources on dynamic models
▸ code.djangoproject.com/wiki/DynamicModels
▸ djangopackages.com/grids/g/forms/
▸ stackoverflow.com/questions/7933596/django-dynamic-model-
fields/7934577
