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django Fake ORM model that query an RestAPI instead of a database —

Project description

==================
django-rest-models
==================

Allow to query a **django** RestAPI with same interface as the django ORM. **(the targeted API must use django-rest-framework + dynamic-rest libraries)**
In fact, it works like any other database engine. You add the rest_models engine in an alternate database and the rest_models databe router.
Then add APIMeta class to the models querying the API, voilà !

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Installation
------------

1. Install using pip:

``pip install django-rest-models``

2. Alternatively, you can download or clone this repo and install with :

``pip install -e .``.

Requirements
------------

This database wrapper work with

- python 2.7, 3.4, 3.5
- django 1.8 , 1.9, 1.10

On the api, this is tested against

- django-rest-framework 3.4, 3.5
- dynamic-rest 1.5, 1.6


Examples
--------

settings.py:

.. code-block:: python

DATABASES = {
'default': {
...
},
'api': {
'ENGINE': 'rest_models.backend',
'NAME': 'https://requestb.in/',
'USER': 'userapi',
'PASSWORD': 'passwordapi',
'AUTH': 'rest_models.backend.auth.BasicAuth',
},
}

DATABASE_ROUTERS = [
'rest_models.router.RestModelRouter',
]


models.py:

.. code-block:: python

class MyModel(models.Model):
field = models.IntegerField()
...

class Meta:
# basic django meta Stuff
verbose_name = 'my model'

# the only customisation that make this model special
class APIMeta:
pass


class MyOtherModel(models.Model):
other_field = models.IntegerField()
first_model = models.ForeignKey(MyModel, db_column='mymodel')
...

class Meta:
# basic django meta Stuff
verbose_name = 'my other model'

# the only customisation that make this model special
class APIMeta:
pass



Targeted API requirements
-------------------------

To allow this database adapter to work like a relational one, the targeted API must respect some requirements :

- dynamic-rest installed and all serializers/views must respectively inherit from Dynamic* (DynamicModelSerializer, etc...)

Each API serializer must :

- Provide the id field
- Provide the related field (ManyToMany and ForeignKey on Models) as DynamicRelationField
- Provide the reverse related field. We must, for each ForeignKey and ManyToMany, add a field on the related model's
serializer.

.. code-block:: python

class MenuSerializer(DynamicModelSerializer):
pizzas = DynamicRelationField('PizzaSerializer', many=True) # Menu.pizza = ManyToMany

class Meta:
model = Menu
name = 'menu'
fields = ('id', 'code', 'name', 'pizzas')
deferred_fields = ('pizza_set', )


class PizzaSerializer(DynamicModelSerializer):

toppings = DynamicRelationField(ToppingSerializer, many=True)
menu = DynamicRelationField(MenuSerializer) # Add this because Menu.pizza = ManyToMany

class Meta:
model = Pizza
name = 'pizza'
fields = ('id', 'name', 'price', 'from_date', 'to_date', 'toppings', 'menu')

django-rest-models provide a way to check the consistency of the api with the local models via the django check framework.
At each startup, it will query the api with OPTIONS to check if the local models match the remote serializers.


Caveats
-------

Since this is not a real relational database, all feature cannot be implemented. Some limitations are inherited by
dynamic-rest filtering system too.

- Aggregations : is not implemented on the api endpoint, maybe in future releases
- Complex filtering using OR : all filter passed to dynamic-rest is ANDed together, so no OR is possible
- Negated AND in filtering: a negated AND give a OR, so previous limitation apply
- Negated OR in filtering: since the compitation of nested filter is complexe and error prone, we disable all OR. in
fact, only some nested of AND is accepted. only the final value of the Q() object can be negated

for short, you **CANNOT** :

.. code-block:: python


Pizza.objects.aggregate()
Pizza.objects.annotate()
Pizza.objects.filter(Q(..) | Q(..))
Pizza.objects.exclude(Q(..) & Q(..))
Pizza.objects.exclude(Q(..) | Q(..))

but you can :

.. code-block:: python

Pizza.objects.create
Pizza.objects.bulk_create
Pizza.objects.update
Pizza.objects.bulk_update
Pizza.objects.select_related
Pizza.objects.prefetch_related
Pizza.objects.values
Pizza.objects.values_list
Pizza.objects.delete
Pizza.objects.count()
Pizza.objects.filter(..., ..., ...)
Pizza.objects.filter(...).filter(...).exclude(...)
Pizza.objects.exclude(..., ...).exclude(...)
Pizza.objects.filter(Q(..) & Q(..))

.. note::

prefetch_related work as expected, but the performance is readly bad. As a matter of fact, a ``Pizza.objects.prefetch_related('toppings')``
will query the toppings for all pizzas as expected, but the query to recover the pizza will contains the linked pizza in the response.
If the database contains a great number of pizzas for the given toppings, the response will contains them all, even if it's
useless at first glance, the linked pizza for each topping is mandotary to django to glue topping <=> pizza relationships.

So, be careful when using prefetch_related.



Specific behaviour
---------------------

Some specific behaviour has been implemented to use the extra feature of a Rest API :

- When inserting, the resulting model is returned by the API. the inserted model is updated with the resulting values.
This imply 2 things:

* If you provided default values for fields in the api, these data will be populated into your created instance if it was ommited.
* If the serializer have some computed data, its data will always be used as a replacement of the one you gave to your
models. (cf example: Pizza.cost which is the sum of the cost of the toppling. after each save, its value will be updated)


Support
-------

This database api support :

- select_related
- order_by
- only
- defer
- filter
- exclude
- delete
- update
- create
- bulk create (with retrive of pk)
- ManyToManyField
- ForeignKey*

.. note::

ForeignKey must have db_column fixed to the name of the reflected field in the api. or all update/create won't use
the value if this field

Documentation
-------------

The full documentation is at http://django-rest-models.readthedocs.org/en/latest/.


Requirements
------------

- Python 2.7, 3.4, 3.5
- Django >= 1.8

Contributions and pull requests are welcome.


Bugs and requests
-----------------

If you found a bug or if you have a request for additional feature, please use the issue tracker on GitHub.

https://github.com/Yupeek/django-rest-models/issues


License
-------

You can use this under GPLv3.

Author
------

Original author: `Darius BERNARD <https://github.com/ornoone>`_.


Thanks
------

Thanks to django for this amazing framework.


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