Metadata-Version: 2.1
Name: django-orm-views
Version: 2.0.0
Summary: A framework for managing database views based on Django, without the migrations
Author: iwoca
Author-email: Josh Dutton <j.dutton@iwoca.co.uk>
License: Copyright 2022 iwoca Ltd
        
        Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
        
        The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
        
        THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
        
Project-URL: Homepage, https://github.com/iwoca/django-orm-views
Project-URL: Bug Tracker, https://github.com/iwoca/django-orm-views/issues
Classifier: Programming Language :: Python :: 3
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Requires-Python: >=3.6
Description-Content-Type: text/markdown
Provides-Extra: test
License-File: LICENSE

# django_orm_views

The package for managing database views using django, without the migrations.
It can be used for generating database views and reading from them using django orm system.

## What does this support?
* This package adds support to Django for **writing** Postgres views using:
  * Raw SQL
  * Django Querysets

They look something like this:

```python
class MySQLView(PostgresViewFromSQL):
    sql = """
       SELECT col_a, col_b FROM table_1;
    """
```

```python
class MyQuerysetView(PostgresViewFromQueryset):
    @classmethod
    def get_queryset(cls):
        return (
            Table1
            .objects
            .values('col_a', 'col_b')
        )
```

* The package allows reading from a view using django ORM. For a view to be readable, it has to be inherited from 
 one of the readable view abstractions - `ReadableViewFromQueryset` or `ReadableViewFromSQL`. It would look like this:
```python

class MyReadableView(ReadableViewFromQueryset):
    @classmethod
    def get_queryset(cls):
        return (
            Table1
            .objects
            .values('col_a', 'col_b')
        )
    
result = MyReadableView.objects.all()
result = MyReadableView.objects.filter(name="test")
result = MyReadableView.objects.get(id=1)
```
The **name** for the view in the database is generated automatically in the base class - `BasePostgresView`.
It's not possible at the moment to define a custom name in the database for a readable view. Though it's possible if the
view is not readable (not inherited from the readable view abstraction).

Since a readable view is basically a not managed django model, you might want to
set some custom meta data for it by defining a Meta class inside the readable view (
For example changing the data source - `db_table`).

**! Note** that defining a custom Meta class is not allowed in the current version of 
the package and will lead to an error!

See some more examples in the tests [here](https://github.com/iwoca/django-orm-views/blob/main/tests/test_project/test_app/postgres_views.py)


This also supports the construction of materialised views via `PostgresMaterialisedViewMixin`. Note that the function `refresh_materialized_view` will
need to be managed by the user in order to keep these up to date where required.
   

## What does this not support?

* Any database engines aside from Postgres (unless syntax happens to be the same!)
* Defining custom name for a readable view in the database. Although it's 
possible for a view that is not readable.
* Defining custom Meta class in a readable view as it can be done for a django model
to define additional settings E.g. `db_table`
## When should I use this?

Our use-case is for a database which is managed by Django
in which we would like to provide an analytics-friendly
representation of some of our data.  This involves giving
analytics direct access to our database (whilst using a
permissions framework), but using views to expose the data
in a more simple way, as well as obscuring data which
we consider personally identifiable/sensitive.

There are other frameworks existing which do similar things,
usually including reads via the ORM.  We found that these
packages all generate migrations (despite being unmanaged)
and we wanted to remove this from the django migrations process
altogether - there seemed to be no value add by including
migrations and they would just muddy our migration states.

## Cool! But how do I use this?

* `pip install django-orm-views`
* Add `'django_orm_views'` to your `INSTALLED_APPS`
* Create a `postgres_views.py` (file or package) inside any app
* Add a `PostgresViewFromQueryset` or `PostgresViewFromSQL` 
to your `postgres_views.py` (as above)
* run `./manage.py sync_views`

A `postgres_views.py` file might look something like the following:

```python
class ComplexViewFromQueryset(PostgresViewFromQueryset):

    prefix = 'test'  # This is optional, but allows you to prefix the table names for views
    
    @classmethod
    def get_queryset(cls):  # Return a `.values` with the query you desire
        return (
            TestModelWithForeignKey
            .objects
            .all()
            .annotate(
                double_integer_col=F('foreign_key__integer_col') * 2
            )
            .values(
                'id',
                'foreign_key__id',
                'foreign_key__integer_col',
                'foreign_key__character_col',
                'foreign_key__date_col',
                'foreign_key__datetime_col',
                'double_integer_col',
            )
        )
```

When we run the `./manage.py sync_views`, we'll create a view called `test_complexviewfromqueryset` under
the `views` schema.

Note, you can put `./manage.py sync_views` into your CI/CD.  It works by:
* Opening a transaction
* Dropping the views schema
* Recreating the views schema
* Recreating all views under that schema
* Committing the transaction

## What's still to come?

* Support for more database engines.  This currently only supports Postgres, 
but should be a reasonably light shift to support other database engines.
* Making the package more configurable using settings.
* Consideration of 0 downtime deployments with views.
  * Note, this can still be achieved with the current implementation,
  but a bad migration (with a view depending) could
  cascade a view and create downtime.  Ideally migrations + 
  view creation should happen in a single transaction.

## Contributing

Feel free to fork the package and propose changes.  The repo comes with a test django project which
can be used to effectively test changes.  It also demonstrates the functionality pretty well.
