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.',
Install Save The Change just like everything else:
$ pip install django-save-the-change
Just add the
SaveTheChange decorator to
from django.db import models from save_the_change.decorators import SaveTheChange @SaveTheChange class Knight(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 encapsulates the fields of your model with its own descriptors
that track their values for any changes. When you call
save(), Save The Change passes the names of
your changed fields through Django’s
update_fields argument, and Django does
the rest, sending only those fields back to the database.
TrackChanges provides some additional
properties and methods to keep interact with changes made to your model,
including comparing the old and new values and reverting any changes to your
model before you save it. It can be used independently
UpdateTogether is an additional decorator
which allows you to specify groups of fields that are dependent on each other in
your model, ensuring that if any of them change they’ll all be saved together.
from django.db import models from save_the_change.decorators import SaveTheChange, UpdateTogether @SaveTheChange @UpdateTogether(('height_feet', 'height_inches')) class Knight(models.model): ...
Now if you ever make a change to either part of our Knight’s height, both the feet and the inches will be sent to the database together, so that they can’t accidentally fall out of sync.