Filtering
=========

Graphene integrates with
`django-filter <https://django-filter.readthedocs.io/en/stable/>`__ to provide filtering of results.
See the `usage documentation <https://django-filter.readthedocs.io/en/stable/guide/usage.html#the-filter>`__
for details on the format for ``filter_fields``.

This filtering is automatically available when implementing a ``relay.Node``.
Additionally ``django-filter`` is an optional dependency of Graphene.

You will need to install it manually, which can be done as follows:

.. code:: bash

    # You'll need to install django-filter
    pip install django-filter>=2

After installing ``django-filter`` you'll need to add the application in the ``settings.py`` file:

.. code:: python

    INSTALLED_APPS = [
        # ...
        "django_filters",
    ]

Note: The techniques below are demoed in the `cookbook example
app <https://github.com/graphql-python/graphene-django/tree/main/examples/cookbook>`__.

Filterable fields
-----------------

The ``filter_fields`` parameter is used to specify the fields which can
be filtered upon. The value specified here is passed directly to
``django-filter``, so see the `filtering
documentation <https://django-filter.readthedocs.io/en/main/guide/usage.html#the-filter>`__
for full details on the range of options available.

For example:

.. code:: python

    class AnimalNode(DjangoObjectType):
        class Meta:
            # Assume you have an Animal model defined with the following fields
            model = Animal
            fields = '__all__'
            filter_fields = ['name', 'genus', 'is_domesticated']
            interfaces = (relay.Node, )

    class Query(ObjectType):
        animal = relay.Node.Field(AnimalNode)
        all_animals = DjangoFilterConnectionField(AnimalNode)

You could then perform a query such as:

.. code::

    query {
      # Note that fields names become camelcased
      allAnimals(genus: "cat", isDomesticated: true) {
        edges {
          node {
            id,
            name
          }
        }
      }
    }

You can also make more complex lookup types available:

.. code:: python

    class AnimalNode(DjangoObjectType):
        class Meta:
            model = Animal
            fields = '__all__'
            # Provide more complex lookup types
            filter_fields = {
                'name': ['exact', 'icontains', 'istartswith'],
                'genus': ['exact'],
                'is_domesticated': ['exact'],
            }
            interfaces = (relay.Node, )

Which you could query as follows:

.. code::

    query {
      # Note that fields names become camelcased
      allAnimals(name_Icontains: "lion") {
        edges {
          node {
            id,
            name
          }
        }
      }
    }

Custom Filtersets
-----------------

By default Graphene provides easy access to the most commonly used
features of ``django-filter``. This is done by transparently creating a
``django_filters.FilterSet`` class for you and passing in the values for
``filter_fields``.

However, you may find this to be insufficient. In these cases you can
create your own ``FilterSet``. You can pass it directly as follows:

.. code:: python

    class AnimalNode(DjangoObjectType):
        class Meta:
            # Assume you have an Animal model defined with the following fields
            model = Animal
            fields = '__all__'
            filter_fields = ['name', 'genus', 'is_domesticated']
            interfaces = (relay.Node, )


    class AnimalFilter(django_filters.FilterSet):
        # Do case-insensitive lookups on 'name'
        name = django_filters.CharFilter(lookup_expr=['iexact'])
        # Allow multiple genera to be selected at once
        genera = django_filters.MultipleChoiceFilter(
            field_name='genus',
            choices=(
                ('Canis', 'Canis'),
                ('Panthera', 'Panthera'),
                ('Seahorse', 'Seahorse')
            )
        )

        class Meta:
            model = Animal
            fields = ['name', 'genus', 'is_domesticated']


    class Query(ObjectType):
        animal = relay.Node.Field(AnimalNode)
        # We specify our custom AnimalFilter using the filterset_class param
        all_animals = DjangoFilterConnectionField(AnimalNode,
                                                  filterset_class=AnimalFilter)


If you were interested in selecting all dogs and cats, you might query as follows:

.. code::

    query {
      allAnimals(genera: ["Canis", "Panthera"]) {
        edges {
          node {
            id,
            name
          }
        }
      }
    }

You can also specify the ``FilterSet`` class using the ``filterset_class``
parameter when defining your ``DjangoObjectType``, however, this can't be used
in unison  with the ``filter_fields`` parameter:

.. code:: python

    class AnimalFilter(django_filters.FilterSet):
        # Do case-insensitive lookups on 'name'
        name = django_filters.CharFilter(lookup_expr=['iexact'])

        class Meta:
            # Assume you have an Animal model defined with the following fields
            model = Animal
            fields = ['name', 'genus', 'is_domesticated']


    class AnimalNode(DjangoObjectType):
        class Meta:
            model = Animal
            fields = '__all__'
            filterset_class = AnimalFilter
            interfaces = (relay.Node, )


    class Query(ObjectType):
        animal = relay.Node.Field(AnimalNode)
        all_animals = DjangoFilterConnectionField(AnimalNode)


The context argument is passed on as the `request argument <http://django-filter.readthedocs.io/en/main/guide/usage.html#request-based-filtering>`__
in a ``django_filters.FilterSet`` instance. You can use this to customize your
filters to be context-dependent. We could modify the ``AnimalFilter`` above to
pre-filter animals owned by the authenticated user (set in ``context.user``).

.. code:: python

    class AnimalFilter(django_filters.FilterSet):
        # Do case-insensitive lookups on 'name'
        name = django_filters.CharFilter(lookup_type=['iexact'])

        class Meta:
            model = Animal
            fields = ['name', 'genus', 'is_domesticated']

        @property
        def qs(self):
            # The query context can be found in self.request.
            return super(AnimalFilter, self).qs.filter(owner=self.request.user)


Ordering
--------

You can use ``OrderFilter`` to define how you want your returned results to be ordered.

Extend the tuple of fields if you want to order by more than one field.

.. code:: python

    from django_filters import FilterSet, OrderingFilter

    class UserFilter(FilterSet):
        class Meta:
            model = UserModel

        order_by = OrderingFilter(
            fields=(
                ('name', 'created_at'),
            )
        )

    class Group(DjangoObjectType):
      users = DjangoFilterConnectionField(Ticket, filterset_class=UserFilter)

      class Meta:
          name = 'Group'
          model = GroupModel
          fields = '__all__'
          interfaces = (relay.Node,)

      def resolve_users(self, info, **kwargs):
        return UserFilter(kwargs).qs


with this set up, you can now order the users under group:

.. code::

    query {
      group(id: "xxx") {
        users(orderBy: "-created_at") {
          xxx
        }
      }
    }


PostgreSQL `ArrayField`
-----------------------

Graphene provides an easy to implement filters on `ArrayField` as they are not natively supported by django_filters:

.. code:: python

    from django.db import models
    from django_filters import FilterSet, OrderingFilter
    from graphene_django.filter import ArrayFilter

    class Event(models.Model):
        name = models.CharField(max_length=50)
        tags = ArrayField(models.CharField(max_length=50))

    class EventFilterSet(FilterSet):
        class Meta:
            model = Event
            fields = {
                "name": ["exact", "contains"],
            }

        tags__contains = ArrayFilter(field_name="tags", lookup_expr="contains")
        tags__overlap = ArrayFilter(field_name="tags", lookup_expr="overlap")
        tags = ArrayFilter(field_name="tags", lookup_expr="exact")

    class EventType(DjangoObjectType):
        class Meta:
            model = Event
            interfaces = (Node,)
            fields = "__all__"
            filterset_class = EventFilterSet

with this set up, you can now filter events by tags:

.. code::

    query {
      events(tags_Overlap: ["concert", "festival"]) {
        name
      }
    }


`TypedFilter`
-------------

Sometimes the automatic detection of the filter input type is not satisfactory for what you are trying to achieve.
You can then explicitly specify the input type you want for your filter by using a `TypedFilter`:

.. code:: python

    from django.db import models
    from django_filters import FilterSet, OrderingFilter
    import graphene
    from graphene_django.filter import TypedFilter

    class Event(models.Model):
        name = models.CharField(max_length=50)

    class EventFilterSet(FilterSet):
        class Meta:
            model = Event
            fields = {
                "name": ["exact", "contains"],
            }

        only_first = TypedFilter(input_type=graphene.Boolean, method="only_first_filter")

        def only_first_filter(self, queryset, _name, value):
            if value:
                return queryset[:1]
            else:
                return queryset

    class EventType(DjangoObjectType):
        class Meta:
            model = Event
            interfaces = (Node,)
            fields = "__all__"
            filterset_class = EventFilterSet