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

Project Description

allow to query an RestAPI (django-rest-framework + dynamic-rest) with same same interface as the django ORM. if fact, it work like any other database engin. you add the rest_models engin in an alternate database, the router, and add a APIMeta class to your models, and let’s go.

stable branche

development status

Installation

  1. Install using pip:

    pip install django-rest-models

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

    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

exemples

settings.py:

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:

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

constraints

to allow this database adaptater to work like a relational one, the API targeted must respect some requirments

  • dynamic-rest installed and all the serializers must provide it’s functionnality (hinerit from DynamicModelSerializer)

each serializers must :

  • provide the id fields
  • provide the related field (ManyToMany and ForeignKey on Models) as DynamicRelationField
  • provide the reverse related field (each ForeignKey and manyToMany add a relation on the other models. the serializer from the other model must provide the DynamicRelationField for these relation
class MenuSerializer(DynamicModelSerializer):
    pizzas = DynamicRelationField('PizzaSerializer', many=True)

    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)

    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.

limitations

since this is not a real relational database, all feathure cannot be implemented. some limitations are inherited by dynamic-rest filtering system too.

  • aggregations : is not implemented on the api endpoint. maybe in future release

  • complexe 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 can’t :

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

but you can :
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 performances is bad. in fact, a Pizza.objects.prefetch_related('toppings') will query the toppings for all pizzas as expeced, but the query to recover the pizza will contains the linked pizza in the response. if the database contains a great lot of pizza 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 relationship.

so, be carefull whene using prefetch_related.

specific comportments

some specific behaviour has been implemented to use the extra functionnality of a Rest API :

  • whene inserting, the resulting model is returned by the API. the inserted model is updated with the resulting values. this imply 2 behavior:
    • if you provided a default data in the api, this data will be populated into your created instance if it was missed
    • if the serializer have some cumputed data, its data will always be used as a replacment of the one you gave to your models. (see exemple 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_colum fixed to the name of the 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 for other Django and Python versions are welcome.

Bugs and requests

If you have found a bug or if you have a request for additional functionality, 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.

Thanks

Thanks to django for this amazing framework.

Release History

Release History

This version
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1.5.1

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1.5.0

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1.4.3

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1.4.2

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1.4.1

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1.4.0

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1.3.0

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1.2.4

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1.2.3

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1.2.2

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1.2.1

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1.2.0

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1.1.0

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1.0.1

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1.0.0

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