Save The Change¶
Save The Change takes this:
>>> lancelot = Knight.objects.get(name="Sir Lancelot")
>>> lancelot.favorite_color = "Blue"
>>> lancelot.save()
And does this:
UPDATE "roundtable_knight"
SET "favorite_color" = 'Blue'
Instead of this:
UPDATE "roundtable_knight"
SET "name" = 'Sir Lancelot',
"from" = 'Camelot',
"quest" = 'To seek the Holy Grail.',
"favorite_color" = 'Blue',
"epithet" = 'The brave',
"actor" = 'John Cleese',
"full_name" = 'John Marwood Cleese',
"height" = '6''11"',
"birth_date" = '1939-10-27',
"birth_union" = 'UK',
"birth_country" = 'England',
"birth_county" = 'Somerset',
"birth_town" = 'Weston-Super-Mare',
"facial_hair" = 'mustache',
"graduated" = true,
"university" = 'Cambridge University',
"degree" = 'LL.B.',
Installation¶
Install Save The Change just like everything else:
$ pip install django-save-the-change
Usage¶
Just add SaveTheChange to your model:
from django.db import models
from save_the_change.mixins import SaveTheChange
class Knight(SaveTheChange, models.model):
...
And that’s it! Keep using Django like you always have, Save The Change will take care of you.
How It Works¶
Save The Change overloads __setattr__ and keeps track of what fields have
changed from their stored value in your database. When you
call save(), Save The Change passes those
changed fields through Django’s update_fields kwarg, and Django does the
rest, sending only those fields back to the database.
Caveats¶
Save The Change can’t help you with ManyToManyFields
nor reverse relations, as those aren’t handled
through save(). But everything else’ll work.
Goodies¶
Save The Change also comes with a second mixin,
TrackChanges. Adding
TrackChanges to your model will expose a few
new properties and methods for tracking and manually reverting changes to your
model before you save it.
You can also use UpdateTogetherModel in place of
Model to add the new field update_together to your
model’s Meta, which allows you to specify that certain fields are dependent on
the values of other fields in your model.