Handle database views. Allow to create migrations for database views. View migrations using django code. They can be reversed. Changes in model view definition are detected automatically. Support almost all options as regular makemigrations command
Project description
django-db-views
How to install?
pip install django-db-views
How to use?
- add
django_db_views
toINSTALLED_APPS
- use
makeviewmigrations
command to create migrations for view models
How to create view in your database?
-
To create your view use DBView class, remember to set view definition attribute.
from django_db_views.db_view import DBView
class Balance(DBView):
virtual_card = models.ForeignKey( VirtualCard, on_delete=models.DO_NOTHING, related_name='virtual_cards' ) total_discount = models.DecimalField(max_digits=12, decimal_places=2) total_returns = models.DecimalField(max_digits=12, decimal_places=2) balance = models.DecimalField(max_digits=12, decimal_places=2) view_definition = """ SELECT row_number() over () as id, # Django requires column called id virtual_card.id as virtual_card_id, sum(...) as total_discount, ... """ class Meta: managed = False db_table = 'virtual_card_balance'
-
The view definition must be a string or a callable. Callable view definition example:
view_definition = lambda: str(SomeModel.objects.all().query)
using callable allow you to write view definition using ORM.
As of version 0.1.0 you can also define view_definition as a dict for multiple engine types. This becomes useful if you use a different engine for local / dev / staging / production. If you do not pass in an engine and have a str or callable the engine will be defaulted to the default database defined in django.settings Example as a dict:
view_definition = {
view_definition = {
"django.db.backends.sqlite3": """
SELECT
row_number() over () as id,
q.id as question_id,
count(*) as total_choices
FROM question q
JOIN choice c on c.question_id = q.id
GROUP BY q.id
""",
"django.db.backends.postgresql": """
SELECT
row_number() over () as id,
q.id as question_id,
count(*) as total_choices
FROM question q
JOIN choice c on c.question_id = q.id
GROUP BY q.id
""",
}
}
How view migrations work?
- DBView working as regular django model. You can use it in any query.
- It's using Django code, view-migrations looks like regular migrations.
- It relies on
db_table
names. makeviewmigrations
command finds previous migration for view.- if there is no such migration then script create a new migration
- if previous migration exists but no change in
view_definition
is detected nothing is done - if previous migration exists, then script will use previous
view_definition
for backward operation, and creates new migration. - when run it will check if the current default engine definined in django.settings is the same engine the view was defined with
Tested with live projects based on Django: 1.11.5, 2.2.10
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