django model 

Recap class SafeUser(models.Model): ! user = models.OneToOneField(User,related_name='safe_user') display_name = models.CharField(null=True, blank=True, max_length=1024) ! def __unicode__(self): return self.user.username + ' ' + self.display_name 

Outline • Good Packages • Model Inheritance • South Experiences • secret behind fields’ parameter 

recommended package • south • django-model-util • django extension 

South • Existing Database need another command to alter the table • South do it for you. • https://docs.djangoproject.com/en/dev/releases/ 1.7/ <— syncdb will be deprecated 

shell_plus • command from djagno extension 

django-model-util • STATUS model • Field Tracker ( previous value of your model) 

Basic • How much Model in an app is appropriate • Can I write raw SQL? • Can I add index? 

Model Inheritance 

Situations of Inheritance • Share Common Parts • Reuse Table • Add Extra Ability 

share Common Part ! • Base Class will not be a table • share common fields between table class CommonInfo(models.Model): name = models.CharField(max_length=100) age = models.PositiveIntegerField() ! class Meta: abstract = True 

multi-table inheritance • Just inherit • will create two table • implicitly using foreign key from django.db import models ! class Place(models.Model): name = models.CharField(max_length=50) address = models.CharField(max_length=80) ! class Restaurant(Place): serves_hot_dogs = models.BooleanField() serves_pizza = models.BooleanField() 

Proxy Model • No Extra Table • add more function class Person(models.Model): first_name = models.CharField(max_length=30) last_name = models.CharField(max_length=30) ! class MyPerson(Person): class Meta: proxy = True ! def do_something(self): # ... pass 

South Issue • After you finish your first version of django app • python manage.py schemamigration app — initial • add migration test if possible 

normalize? • denormalized carefully 

Concern Cache • Concern Cache first. than the De-normalize • CH20 discuss more about reducing bottle neck 

Fields • Blank is logical, for validation • null is related to how database save empty value • any field without null=True specified in the model needs to have a value set (from Malcolm) 

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Manager • Looking very good • More Readable 

You have two choice 

the reason • First manager will be used by django 

Summary • Start normalized • Don’t forget to use indexes. • Watch out for the “gotchas” when using the null=True and blank=True • model inheritance