.. _django_range_fields_desc:

===================================================
**Range Fields** description
===================================================

.. seealso::

   - https://docs.djangoproject.com/en/dev/ref/contrib/postgres/fields/#range-fields
   - https://docs.djangoproject.com/fr/3.0/ref/contrib/postgres/fields/
   - https://github.com/django/django/blob/master/docs/ref/contrib/postgres/fields.txt
   - :ref:`postgresql_range_types`


.. contents::
   :depth: 3

Introduction
=============

There are **five range field types**, corresponding to the built-in :ref:`range types <postgresql_range_types>`
in PostgreSQL.

These fields are used to store a range of values; for example the start and end
timestamps of an event, or the range of ages an activity is suitable for.

All of the range fields translate to :ref:`psycopg2 Range objects <psycopg2:adapt-range>`
in Python, but also accept tuples as input if no bounds information is necessary.

The default is lower bound included, upper bound excluded; that is, ``[)``.


Querying Range Fields
========================

There are a number of custom lookups and transforms for range fields. They are
available on all the above fields, but we will use the following example
model::

    from django.contrib.postgres.fields import IntegerRangeField
    from django.db import models

    class Event(models.Model):
        name = models.CharField(max_length=200)
        ages = IntegerRangeField()
        start = models.DateTimeField()

        def __str__(self):
            return self.name

We will also use the following example objects::

    >>> import datetime
    >>> from django.utils import timezone
    >>> now = timezone.now()
    >>> Event.objects.create(name='Soft play', ages=(0, 10), start=now)
    >>> Event.objects.create(name='Pub trip', ages=(21, None), start=now - datetime.timedelta(days=1))

and ``NumericRange``:

    >>> from psycopg2.extras import NumericRange

Containment functions
========================

As with other PostgreSQL fields, there are three standard containment
operators: ``contains``, ``contained_by`` and ``overlap``, using the SQL
operators ``@>``, ``<@``, and ``&&`` respectively.

``contains``
---------------

::

    >>> Event.objects.filter(ages__contains=NumericRange(4, 5))
    <QuerySet [<Event: Soft play>]>


``contained_by``
-------------------

::

    >>> Event.objects.filter(ages__contained_by=NumericRange(0, 15))
    <QuerySet [<Event: Soft play>]>

The ``contained_by`` lookup is also available on the non-range field types:
:class:`~django.db.models.SmallAutoField`,
:class:`~django.db.models.AutoField`, :class:`~django.db.models.BigAutoField`,
:class:`~django.db.models.SmallIntegerField`,
:class:`~django.db.models.IntegerField`,
:class:`~django.db.models.BigIntegerField`,
:class:`~django.db.models.DecimalField`, :class:`~django.db.models.FloatField`,
:class:`~django.db.models.DateField`, and
:class:`~django.db.models.DateTimeField`. For example::

    >>> from psycopg2.extras import DateTimeTZRange
    >>> Event.objects.filter(start__contained_by=DateTimeTZRange(
    ...     timezone.now() - datetime.timedelta(hours=1),
    ...     timezone.now() + datetime.timedelta(hours=1),
    ... )
    <QuerySet [<Event: Soft play>]>

.. versionchanged:: 3.1

    Support for :class:`~django.db.models.SmallAutoField`,
    :class:`~django.db.models.AutoField`,
    :class:`~django.db.models.BigAutoField`,
    :class:`~django.db.models.SmallIntegerField`, and
    :class:`~django.db.models.DecimalField` was added.


``overlap``
-------------

    >>> Event.objects.filter(ages__overlap=NumericRange(8, 12))
    <QuerySet [<Event: Soft play>]>

Comparison functions
======================

Range fields support the standard lookups: `lt`, `gt`, `lte` and `gte`.

These are not particularly helpful - they compare the lower bounds first and then
the upper bounds only if necessary.

This is also the strategy used to order by a range field.
It is better to use the specific range comparison operators.


``fully_lt``
---------------

The returned ranges are strictly less than the passed range. In other words,
all the points in the returned range are less than all those in the passed
range.

    >>> Event.objects.filter(ages__fully_lt=NumericRange(11, 15))
    <QuerySet [<Event: Soft play>]>


``fully_gt``
-------------

The returned ranges are strictly greater than the passed range. In other words,
the all the points in the returned range are greater than all those in the
passed range.

    >>> Event.objects.filter(ages__fully_gt=NumericRange(11, 15))
    <QuerySet [<Event: Pub trip>]>


``not_lt``
------------

The returned ranges do not contain any points less than the passed range, that
is the lower bound of the returned range is at least the lower bound of the
passed range.

    >>> Event.objects.filter(ages__not_lt=NumericRange(0, 15))
    <QuerySet [<Event: Soft play>, <Event: Pub trip>]>


``not_gt``
------------

The returned ranges do not contain any points greater than the passed range, that
is the upper bound of the returned range is at most the upper bound of the
passed range.

    >>> Event.objects.filter(ages__not_gt=NumericRange(3, 10))
    <QuerySet [<Event: Soft play>]>


``adjacent_to``
---------------

The returned ranges share a bound with the passed range.

    >>> Event.objects.filter(ages__adjacent_to=NumericRange(10, 21))
    <QuerySet [<Event: Soft play>, <Event: Pub trip>]>



.. _range_fields_querying_bounds:

Querying using the bounds
=============================

There are three transforms available for use in queries. You can extract the
lower or upper bound, or query based on emptiness.


``startswith``
-----------------

Returned objects have the given lower bound. Can be chained to valid lookups
for the base field.

    >>> Event.objects.filter(ages__startswith=21)
    <QuerySet [<Event: Pub trip>]>


``endswith``
-------------

Returned objects have the given upper bound. Can be chained to valid lookups
for the base field.

    >>> Event.objects.filter(ages__endswith=10)
    <QuerySet [<Event: Soft play>]>


``isempty``
-------------

Returned objects are empty ranges.
Can be chained to valid lookups for a :class:`~django.db.models.BooleanField`.

    >>> Event.objects.filter(ages__isempty=True)
    <QuerySet []>


``lower_inc``
--------------

.. versionadded:: 3.1

Returns objects that have inclusive or exclusive lower bounds, depending on the
boolean value passed. Can be chained to valid lookups for a
:class:`~django.db.models.BooleanField`.

    >>> Event.objects.filter(ages__lower_inc=True)
    <QuerySet [<Event: Soft play>, <Event: Pub trip>]>


``lower_inf``
--------------------

.. versionadded:: 3.1

Returns objects that have unbounded (infinite) or bounded lower bound,
depending on the boolean value passed. Can be chained to valid lookups for a
:class:`~django.db.models.BooleanField`.

    >>> Event.objects.filter(ages__lower_inf=True)
    <QuerySet []>


``upper_inc``
---------------

.. versionadded:: 3.1

Returns objects that have inclusive or exclusive upper bounds, depending on the
boolean value passed. Can be chained to valid lookups for a
:class:`~django.db.models.BooleanField`.

    >>> Event.objects.filter(ages__upper_inc=True)
    <QuerySet []>


``upper_inf``
----------------

.. versionadded:: 3.1

Returns objects that have unbounded (infinite) or bounded upper bound,
depending on the boolean value passed. Can be chained to valid lookups for a
:class:`~django.db.models.BooleanField`.

    >>> Event.objects.filter(ages__upper_inf=True)
    <QuerySet [<Event: Pub trip>]>

Defining your own range types
=================================

**PostgreSQL allows the definition of custom range types**.

Django's model and form field implementations use base classes below, and psycopg2
provides a :func:`~psycopg2:psycopg2.extras.register_range` to allow use of
custom range types.

.. class:: RangeField(**options)

    Base class for model range fields.

    .. attribute:: base_field

        The model field class to use.

    .. attribute:: range_type

        The psycopg2 range type to use.

    .. attribute:: form_field

        The form field class to use. Should be a subclass of
        :class:`django.contrib.postgres.forms.BaseRangeField`.

.. class:: django.contrib.postgres.forms.BaseRangeField

    Base class for form range fields.

    .. attribute:: base_field

        The form field to use.

    .. attribute:: range_type

        The psycopg2 range type to use.