testbed/django__django/docs/ref/contrib/postgres/fields.txt

================================
PostgreSQL specific model fields
================================

All of these fields are available from the ``django.contrib.postgres.fields``
module.

.. currentmodule:: django.contrib.postgres.fields

Indexing these fields
=====================

:class:`~django.db.models.Index` and :attr:`.Field.db_index` both create a
B-tree index, which isn't particularly helpful when querying complex data types.
Indexes such as :class:`~django.contrib.postgres.indexes.GinIndex` and
:class:`~django.contrib.postgres.indexes.GistIndex` are better suited, though
the index choice is dependent on the queries that you're using. Generally, GiST
may be a good choice for the :ref:`range fields <range-fields>` and
:class:`HStoreField`, and GIN may be helpful for :class:`ArrayField`.

``ArrayField``
==============

.. class:: ArrayField(base_field, size=None, **options)

    A field for storing lists of data. Most field types can be used, and you
    pass another field instance as the :attr:`base_field
    <ArrayField.base_field>`. You may also specify a :attr:`size
    <ArrayField.size>`. ``ArrayField`` can be nested to store multi-dimensional
    arrays.

    If you give the field a :attr:`~django.db.models.Field.default`, ensure
    it's a callable such as ``list`` (for an empty default) or a callable that
    returns a list (such as a function). Incorrectly using ``default=[]``
    creates a mutable default that is shared between all instances of
    ``ArrayField``.

    .. attribute:: base_field

        This is a required argument.

        Specifies the underlying data type and behavior for the array. It
        should be an instance of a subclass of
        :class:`~django.db.models.Field`. For example, it could be an
        :class:`~django.db.models.IntegerField` or a
        :class:`~django.db.models.CharField`. Most field types are permitted,
        with the exception of those handling relational data
        (:class:`~django.db.models.ForeignKey`,
        :class:`~django.db.models.OneToOneField` and
        :class:`~django.db.models.ManyToManyField`) and file fields (
        :class:`~django.db.models.FileField` and
        :class:`~django.db.models.ImageField`).

        It is possible to nest array fields - you can specify an instance of
        ``ArrayField`` as the ``base_field``. For example::

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


            class ChessBoard(models.Model):
                board = ArrayField(
                    ArrayField(
                        models.CharField(max_length=10, blank=True),
                        size=8,
                    ),
                    size=8,
                )

        Transformation of values between the database and the model, validation
        of data and configuration, and serialization are all delegated to the
        underlying base field.

    .. attribute:: size

        This is an optional argument.

        If passed, the array will have a maximum size as specified. This will
        be passed to the database, although PostgreSQL at present does not
        enforce the restriction.

.. note::

    When nesting ``ArrayField``, whether you use the ``size`` parameter or not,
    PostgreSQL requires that the arrays are rectangular::

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


        class Board(models.Model):
            pieces = ArrayField(ArrayField(models.IntegerField()))


        # Valid
        Board(
            pieces=[
                [2, 3],
                [2, 1],
            ]
        )

        # Not valid
        Board(
            pieces=[
                [2, 3],
                [2],
            ]
        )

    If irregular shapes are required, then the underlying field should be made
    nullable and the values padded with ``None``.

Querying ``ArrayField``
-----------------------

There are a number of custom lookups and transforms for :class:`ArrayField`.
We will use the following example model::

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


    class Post(models.Model):
        name = models.CharField(max_length=200)
        tags = ArrayField(models.CharField(max_length=200), blank=True)

        def __str__(self):
            return self.name

.. fieldlookup:: arrayfield.contains

``contains``
~~~~~~~~~~~~

The :lookup:`contains` lookup is overridden on :class:`ArrayField`. The
returned objects will be those where the values passed are a subset of the
data. It uses the SQL operator ``@>``. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts"])
    >>> Post.objects.create(name="Third post", tags=["tutorial", "django"])

    >>> Post.objects.filter(tags__contains=["thoughts"])
    <QuerySet [<Post: First post>, <Post: Second post>]>

    >>> Post.objects.filter(tags__contains=["django"])
    <QuerySet [<Post: First post>, <Post: Third post>]>

    >>> Post.objects.filter(tags__contains=["django", "thoughts"])
    <QuerySet [<Post: First post>]>

.. fieldlookup:: arrayfield.contained_by

``contained_by``
~~~~~~~~~~~~~~~~

This is the inverse of the :lookup:`contains <arrayfield.contains>` lookup -
the objects returned will be those where the data is a subset of the values
passed. It uses the SQL operator ``<@``. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts"])
    >>> Post.objects.create(name="Third post", tags=["tutorial", "django"])

    >>> Post.objects.filter(tags__contained_by=["thoughts", "django"])
    <QuerySet [<Post: First post>, <Post: Second post>]>

    >>> Post.objects.filter(tags__contained_by=["thoughts", "django", "tutorial"])
    <QuerySet [<Post: First post>, <Post: Second post>, <Post: Third post>]>

.. fieldlookup:: arrayfield.overlap

``overlap``
~~~~~~~~~~~

Returns objects where the data shares any results with the values passed. Uses
the SQL operator ``&&``. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts", "tutorial"])
    >>> Post.objects.create(name="Third post", tags=["tutorial", "django"])

    >>> Post.objects.filter(tags__overlap=["thoughts"])
    <QuerySet [<Post: First post>, <Post: Second post>]>

    >>> Post.objects.filter(tags__overlap=["thoughts", "tutorial"])
    <QuerySet [<Post: First post>, <Post: Second post>, <Post: Third post>]>

    >>> Post.objects.filter(tags__overlap=Post.objects.values_list("tags"))
    <QuerySet [<Post: First post>, <Post: Second post>, <Post: Third post>]>

.. versionchanged:: 4.2

    Support for ``QuerySet.values()`` and ``values_list()`` as a right-hand
    side was added.

.. fieldlookup:: arrayfield.len

``len``
~~~~~~~

Returns the length of the array. The lookups available afterward are those
available for :class:`~django.db.models.IntegerField`. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts"])

    >>> Post.objects.filter(tags__len=1)
    <QuerySet [<Post: Second post>]>

.. fieldlookup:: arrayfield.index

Index transforms
~~~~~~~~~~~~~~~~

Index transforms index into the array. Any non-negative integer can be used.
There are no errors if it exceeds the :attr:`size <ArrayField.size>` of the
array. The lookups available after the transform are those from the
:attr:`base_field <ArrayField.base_field>`. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts"])

    >>> Post.objects.filter(tags__0="thoughts")
    <QuerySet [<Post: First post>, <Post: Second post>]>

    >>> Post.objects.filter(tags__1__iexact="Django")
    <QuerySet [<Post: First post>]>

    >>> Post.objects.filter(tags__276="javascript")
    <QuerySet []>

.. note::

    PostgreSQL uses 1-based indexing for array fields when writing raw SQL.
    However these indexes and those used in :lookup:`slices <arrayfield.slice>`
    use 0-based indexing to be consistent with Python.

.. fieldlookup:: arrayfield.slice

Slice transforms
~~~~~~~~~~~~~~~~

Slice transforms take a slice of the array. Any two non-negative integers can
be used, separated by a single underscore. The lookups available after the
transform do not change. For example:

.. code-block:: pycon

    >>> Post.objects.create(name="First post", tags=["thoughts", "django"])
    >>> Post.objects.create(name="Second post", tags=["thoughts"])
    >>> Post.objects.create(name="Third post", tags=["django", "python", "thoughts"])

    >>> Post.objects.filter(tags__0_1=["thoughts"])
    <QuerySet [<Post: First post>, <Post: Second post>]>

    >>> Post.objects.filter(tags__0_2__contains=["thoughts"])
    <QuerySet [<Post: First post>, <Post: Second post>]>

.. note::

    PostgreSQL uses 1-based indexing for array fields when writing raw SQL.
    However these slices and those used in :lookup:`indexes <arrayfield.index>`
    use 0-based indexing to be consistent with Python.

.. admonition:: Multidimensional arrays with indexes and slices

    PostgreSQL has some rather esoteric behavior when using indexes and slices
    on multidimensional arrays. It will always work to use indexes to reach
    down to the final underlying data, but most other slices behave strangely
    at the database level and cannot be supported in a logical, consistent
    fashion by Django.

``CIText`` fields
=================

.. class:: CIText(**options)

    .. deprecated:: 4.2

    A mixin to create case-insensitive text fields backed by the citext_ type.
    Read about `the performance considerations`_ prior to using it.

    To use ``citext``, use the :class:`.CITextExtension` operation to
    :ref:`set up the citext extension <create-postgresql-extensions>` in
    PostgreSQL before the first ``CreateModel`` migration operation.

    If you're using an :class:`~django.contrib.postgres.fields.ArrayField`
    of ``CIText`` fields, you must add ``'django.contrib.postgres'`` in your
    :setting:`INSTALLED_APPS`, otherwise field values will appear as strings
    like ``'{thoughts,django}'``.

    Several fields that use the mixin are provided:

.. class:: CICharField(**options)

    .. deprecated:: 4.2

        ``CICharField`` is deprecated in favor of
        ``CharField(db_collation="…")`` with a case-insensitive
        non-deterministic collation.

.. class:: CIEmailField(**options)

    .. deprecated:: 4.2

        ``CIEmailField`` is deprecated in favor of
        ``EmailField(db_collation="…")`` with a case-insensitive
        non-deterministic collation.

.. class:: CITextField(**options)

    .. deprecated:: 4.2

        ``CITextField`` is deprecated in favor of
        ``TextField(db_collation="…")`` with a case-insensitive
        non-deterministic collation.

    These fields subclass :class:`~django.db.models.CharField`,
    :class:`~django.db.models.EmailField`, and
    :class:`~django.db.models.TextField`, respectively.

    ``max_length`` won't be enforced in the database since ``citext`` behaves
    similar to PostgreSQL's ``text`` type.

    .. _citext: https://www.postgresql.org/docs/current/citext.html
    .. _the performance considerations: https://www.postgresql.org/docs/current/citext.html#id-1.11.7.19.9

.. admonition:: Case-insensitive collations

    It's preferable to use non-deterministic collations instead of the
    ``citext`` extension. You can create them using the
    :class:`~django.contrib.postgres.operations.CreateCollation` migration
    operation. For more details, see :ref:`manage-postgresql-collations` and
    the PostgreSQL documentation about `non-deterministic collations`_.

    .. _non-deterministic collations: https://www.postgresql.org/docs/current/collation.html#COLLATION-NONDETERMINISTIC

``HStoreField``
===============

.. class:: HStoreField(**options)

    A field for storing key-value pairs. The Python data type used is a
    ``dict``. Keys must be strings, and values may be either strings or nulls
    (``None`` in Python).

    To use this field, you'll need to:

    #. Add ``'django.contrib.postgres'`` in your :setting:`INSTALLED_APPS`.
    #. :ref:`Set up the hstore extension <create-postgresql-extensions>` in
       PostgreSQL.

    You'll see an error like ``can't adapt type 'dict'`` if you skip the first
    step, or ``type "hstore" does not exist`` if you skip the second.

.. note::

    On occasions it may be useful to require or restrict the keys which are
    valid for a given field. This can be done using the
    :class:`~django.contrib.postgres.validators.KeysValidator`.

Querying ``HStoreField``
------------------------

In addition to the ability to query by key, there are a number of custom
lookups available for ``HStoreField``.

We will use the following example model::

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


    class Dog(models.Model):
        name = models.CharField(max_length=200)
        data = HStoreField()

        def __str__(self):
            return self.name

.. fieldlookup:: hstorefield.key

Key lookups
~~~~~~~~~~~

To query based on a given key, you can use that key as the lookup name:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie"})

    >>> Dog.objects.filter(data__breed="collie")
    <QuerySet [<Dog: Meg>]>

You can chain other lookups after key lookups:

.. code-block:: pycon

    >>> Dog.objects.filter(data__breed__contains="l")
    <QuerySet [<Dog: Rufus>, <Dog: Meg>]>

or use ``F()`` expressions to annotate a key value. For example:

.. code-block:: pycon

    >>> from django.db.models import F
    >>> rufus = Dog.objects.annotate(breed=F("data__breed"))[0]
    >>> rufus.breed
    'labrador'

If the key you wish to query by clashes with the name of another lookup, you
need to use the :lookup:`hstorefield.contains` lookup instead.

.. note::

    Key transforms can also be chained with: :lookup:`contains`,
    :lookup:`icontains`, :lookup:`endswith`, :lookup:`iendswith`,
    :lookup:`iexact`, :lookup:`regex`, :lookup:`iregex`, :lookup:`startswith`,
    and :lookup:`istartswith` lookups.

.. warning::

    Since any string could be a key in a hstore value, any lookup other than
    those listed below will be interpreted as a key lookup. No errors are
    raised. Be extra careful for typing mistakes, and always check your queries
    work as you intend.

.. fieldlookup:: hstorefield.contains

``contains``
~~~~~~~~~~~~

The :lookup:`contains` lookup is overridden on
:class:`~django.contrib.postgres.fields.HStoreField`. The returned objects are
those where the given ``dict`` of key-value pairs are all contained in the
field. It uses the SQL operator ``@>``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador", "owner": "Bob"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})
    >>> Dog.objects.create(name="Fred", data={})

    >>> Dog.objects.filter(data__contains={"owner": "Bob"})
    <QuerySet [<Dog: Rufus>, <Dog: Meg>]>

    >>> Dog.objects.filter(data__contains={"breed": "collie"})
    <QuerySet [<Dog: Meg>]>

.. fieldlookup:: hstorefield.contained_by

``contained_by``
~~~~~~~~~~~~~~~~

This is the inverse of the :lookup:`contains <hstorefield.contains>` lookup -
the objects returned will be those where the key-value pairs on the object are
a subset of those in the value passed. It uses the SQL operator ``<@``. For
example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador", "owner": "Bob"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})
    >>> Dog.objects.create(name="Fred", data={})

    >>> Dog.objects.filter(data__contained_by={"breed": "collie", "owner": "Bob"})
    <QuerySet [<Dog: Meg>, <Dog: Fred>]>

    >>> Dog.objects.filter(data__contained_by={"breed": "collie"})
    <QuerySet [<Dog: Fred>]>

.. fieldlookup:: hstorefield.has_key

``has_key``
~~~~~~~~~~~

Returns objects where the given key is in the data. Uses the SQL operator
``?``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})

    >>> Dog.objects.filter(data__has_key="owner")
    <QuerySet [<Dog: Meg>]>

.. fieldlookup:: hstorefield.has_any_keys

``has_any_keys``
~~~~~~~~~~~~~~~~

Returns objects where any of the given keys are in the data. Uses the SQL
operator ``?|``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador"})
    >>> Dog.objects.create(name="Meg", data={"owner": "Bob"})
    >>> Dog.objects.create(name="Fred", data={})

    >>> Dog.objects.filter(data__has_any_keys=["owner", "breed"])
    <QuerySet [<Dog: Rufus>, <Dog: Meg>]>

.. fieldlookup:: hstorefield.has_keys

``has_keys``
~~~~~~~~~~~~

Returns objects where all of the given keys are in the data. Uses the SQL operator
``?&``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})

    >>> Dog.objects.filter(data__has_keys=["breed", "owner"])
    <QuerySet [<Dog: Meg>]>

.. fieldlookup:: hstorefield.keys

``keys``
~~~~~~~~

Returns objects where the array of keys is the given value. Note that the order
is not guaranteed to be reliable, so this transform is mainly useful for using
in conjunction with lookups on
:class:`~django.contrib.postgres.fields.ArrayField`. Uses the SQL function
``akeys()``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"toy": "bone"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})

    >>> Dog.objects.filter(data__keys__overlap=["breed", "toy"])
    <QuerySet [<Dog: Rufus>, <Dog: Meg>]>

.. fieldlookup:: hstorefield.values

``values``
~~~~~~~~~~

Returns objects where the array of values is the given value. Note that the
order is not guaranteed to be reliable, so this transform is mainly useful for
using in conjunction with lookups on
:class:`~django.contrib.postgres.fields.ArrayField`. Uses the SQL function
``avals()``. For example:

.. code-block:: pycon

    >>> Dog.objects.create(name="Rufus", data={"breed": "labrador"})
    >>> Dog.objects.create(name="Meg", data={"breed": "collie", "owner": "Bob"})

    >>> Dog.objects.filter(data__values__contains=["collie"])
    <QuerySet [<Dog: Meg>]>

.. _range-fields:

Range Fields
============

There are five range field types, corresponding to the built-in 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:`psycopg Range objects
<psycopg: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 ``[)`` (see the PostgreSQL documentation for details about
`different bounds`_). The default bounds can be changed for non-discrete range
fields (:class:`.DateTimeRangeField` and :class:`.DecimalRangeField`) by using
the ``default_bounds`` argument.

``IntegerRangeField``
---------------------

.. class:: IntegerRangeField(**options)

    Stores a range of integers. Based on an
    :class:`~django.db.models.IntegerField`. Represented by an ``int4range`` in
    the database and a
    ``django.db.backends.postgresql.psycopg_any.NumericRange`` in Python.

    Regardless of the bounds specified when saving the data, PostgreSQL always
    returns a range in a canonical form that includes the lower bound and
    excludes the upper bound, that is ``[)``.

``BigIntegerRangeField``
------------------------

.. class:: BigIntegerRangeField(**options)

    Stores a range of large integers. Based on a
    :class:`~django.db.models.BigIntegerField`. Represented by an ``int8range``
    in the database and a
    ``django.db.backends.postgresql.psycopg_any.NumericRange`` in Python.

    Regardless of the bounds specified when saving the data, PostgreSQL always
    returns a range in a canonical form that includes the lower bound and
    excludes the upper bound, that is ``[)``.

``DecimalRangeField``
---------------------

.. class:: DecimalRangeField(default_bounds='[)', **options)

    Stores a range of floating point values. Based on a
    :class:`~django.db.models.DecimalField`. Represented by a ``numrange`` in
    the database and a
    ``django.db.backends.postgresql.psycopg_any.NumericRange`` in Python.

    .. attribute:: DecimalRangeField.default_bounds

        Optional. The value of ``bounds`` for list and tuple inputs. The
        default is lower bound included, upper bound excluded, that is ``[)``
        (see the PostgreSQL documentation for details about
        `different bounds`_). ``default_bounds`` is not used for
        ``django.db.backends.postgresql.psycopg_any.NumericRange`` inputs.

``DateTimeRangeField``
----------------------

.. class:: DateTimeRangeField(default_bounds='[)', **options)

    Stores a range of timestamps. Based on a
    :class:`~django.db.models.DateTimeField`. Represented by a ``tstzrange`` in
    the database and a
    ``django.db.backends.postgresql.psycopg_any.DateTimeTZRange`` in Python.

    .. attribute:: DateTimeRangeField.default_bounds

        Optional. The value of ``bounds`` for list and tuple inputs. The
        default is lower bound included, upper bound excluded, that is ``[)``
        (see the PostgreSQL documentation for details about
        `different bounds`_). ``default_bounds`` is not used for
        ``django.db.backends.postgresql.psycopg_any.DateTimeTZRange`` inputs.

``DateRangeField``
------------------

.. class:: DateRangeField(**options)

    Stores a range of dates. Based on a
    :class:`~django.db.models.DateField`. Represented by a ``daterange`` in the
    database and a ``django.db.backends.postgresql.psycopg_any.DateRange`` in
    Python.

    Regardless of the bounds specified when saving the data, PostgreSQL always
    returns a range in a canonical form that includes the lower bound and
    excludes the upper bound, 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:

.. code-block:: pycon

    >>> 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 django.db.backends.postgresql.psycopg_any 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.

.. fieldlookup:: rangefield.contains

``contains``
^^^^^^^^^^^^

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

.. fieldlookup:: rangefield.contained_by

``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:

.. code-block:: pycon

    >>> from django.db.backends.postgresql.psycopg_any 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>]>

.. fieldlookup:: rangefield.overlap

``overlap``
^^^^^^^^^^^

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

Comparison functions
~~~~~~~~~~~~~~~~~~~~

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

.. fieldlookup:: rangefield.fully_lt

``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>]>

.. fieldlookup:: rangefield.fully_gt

``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>]>

.. fieldlookup:: rangefield.not_lt

``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>]>

.. fieldlookup:: rangefield.not_gt

``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>]>

.. fieldlookup:: rangefield.adjacent_to

``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>]>

Querying using the bounds
~~~~~~~~~~~~~~~~~~~~~~~~~

Range fields support several extra lookups.

.. fieldlookup:: rangefield.startswith

``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>]>

.. fieldlookup:: rangefield.endswith

``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>]>

.. fieldlookup:: rangefield.isempty

``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 []>

.. fieldlookup:: rangefield.lower_inc

``lower_inc``
^^^^^^^^^^^^^

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>]>

.. fieldlookup:: rangefield.lower_inf

``lower_inf``
^^^^^^^^^^^^^

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 []>

.. fieldlookup:: rangefield.upper_inc

``upper_inc``
^^^^^^^^^^^^^

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 []>

.. fieldlookup:: rangefield.upper_inf

``upper_inf``
^^^^^^^^^^^^^

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 ``psycopg`` provides a
:func:`~psycopg:psycopg.types.range.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 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 range type to use.

Range operators
---------------

.. class:: RangeOperators

PostgreSQL provides a set of SQL operators that can be used together with the
range data types (see `the PostgreSQL documentation for the full details of
range operators <https://www.postgresql.org/docs/current/
functions-range.html#RANGE-OPERATORS-TABLE>`_). This class is meant as a
convenient method to avoid typos. The operator names overlap with the names of
corresponding lookups.

.. code-block:: python

    class RangeOperators:
        EQUAL = "="
        NOT_EQUAL = "<>"
        CONTAINS = "@>"
        CONTAINED_BY = "<@"
        OVERLAPS = "&&"
        FULLY_LT = "<<"
        FULLY_GT = ">>"
        NOT_LT = "&>"
        NOT_GT = "&<"
        ADJACENT_TO = "-|-"

RangeBoundary() expressions
---------------------------

.. class:: RangeBoundary(inclusive_lower=True, inclusive_upper=False)

    .. attribute:: inclusive_lower

        If ``True`` (default), the lower bound is inclusive ``'['``, otherwise
        it's exclusive ``'('``.

    .. attribute:: inclusive_upper

        If ``False`` (default), the upper bound is exclusive ``')'``, otherwise
        it's inclusive ``']'``.

A ``RangeBoundary()`` expression represents the range boundaries. It can be
used with a custom range functions that expected boundaries, for example to
define :class:`~django.contrib.postgres.constraints.ExclusionConstraint`. See
`the PostgreSQL documentation for the full details <https://www.postgresql.org/
docs/current/rangetypes.html#RANGETYPES-INCLUSIVITY>`_.

.. _different bounds: https://www.postgresql.org/docs/current/rangetypes.html#RANGETYPES-IO