/django-db-views

Creating automatic migrations for Views models witch working reverse and full command options like in normal makemigrations

Primary LanguagePythonMIT LicenseMIT

django-db-views

How to install?

  • pip install django-db-views

How to use?

  • add django_db_views to INSTALLED_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.

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.

Tested with live projects based on Django: 1.11.5, 2.2.10