# Django 1.8.18.dev20170123152445 documentation

# PostgreSQL specific model fields

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

## ArrayField

class `ArrayField`(base_field, size=None, **options)

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

  If you give the field a `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`.

  `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 `Field`. For example, it could be an `IntegerField` or a `CharField`. Most field types are permitted, with the exception of those handling relational data (`ForeignKey`, `OneToOneField` and `ManyToManyField`).

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

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

        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.

  `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 `ArrayField`. We will use the following example model:

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

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

        def __str__(self):  # __unicode__ on Python 2
            return self.name

#### contains

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

    >>> 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'])
    [<Post: First post>, <Post: Second post>]

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

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

#### contained_by

This is the inverse of the `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:

    >>> 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'])
    [<Post: First post>, <Post: Second post>]

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

#### overlap

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

    >>> 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__overlap=['thoughts'])
    [<Post: First post>, <Post: Second post>]

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

#### len

Returns the length of the array. The lookups available afterwards are those available for `IntegerField`. For example:

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

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

#### Index transforms

This class of transforms allows you to index into the array in queries. Any non-negative integer can be used. There are no errors if it exceeds the `size` of the array. The lookups available after the transform are those from the `base_field`. For example:

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

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

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

    >>> Post.objects.filter(tags__276='javascript')
    []

Note

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

#### Slice transforms

This class of transforms allow you to 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:

    >>> 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'])
    [<Post: First post>, <Post: Second post>]

    >>> Post.objects.filter(tags__0_2__contains=['thoughts'])
    [<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 `indexes` use 0-based indexing to be consistent with Python.

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.

### Indexing ArrayField

At present using `db_index` will create a `btree` index. This does not offer particularly significant help to querying. A more useful index is a `GIN` index, which you should create using a `RunSQL` operation.

## HStoreField

class `HStoreField`(**options)

  A field for storing mappings of strings to strings. The Python data type used is a `dict`.

  To use this field, you’ll need to:

  1. Add `'django.contrib.postgres'` in your `INSTALLED_APPS`.

  2. Setup the hstore extension in PostgreSQL before the first `CreateModel` or `AddField` operation by adding a migration with the `HStoreExtension` operation. For example:

         from django.contrib.postgres.operations import HStoreExtension

         class Migration(migrations.Migration):
             ...

             operations = [
                 HStoreExtension(),
                 ...
             ]

     Creating the extension requires a database user with superuser privileges. If the Django database user doesn’t have superuser privileges, you’ll have to create the extension outside of Django migrations with a user that has the appropriate privileges. In that case, connect to your Django database and run the query `CREATE EXTENSION IF NOT EXISTS hstore;`

  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 `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):  # __unicode__ on Python 2
            return self.name

#### Key lookups

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

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

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

You can chain other lookups after key lookups:

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

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

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.

#### contains

The `contains` lookup is overridden on `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:

    >>> 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'})
    [<Dog: Rufus>, <Dog: Meg>]

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

#### contained_by

This is the inverse of the `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:

    >>> 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'})
    [<Dog: Meg>, <Dog: Fred>]

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

#### has_key

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

    >>> 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')
    [<Dog: Meg>]

#### has_keys

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

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

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

#### 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 `ArrayField`. Uses the SQL function `akeys()`. For example:

    >>> 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'])
    [<Dog: Rufus>, <Dog: Meg>]

#### 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 `ArrayField`. Uses the SQL function `avalues()`. For example:

    >>> 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'])
    [<Dog: Meg>]

## 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 psycopg2 Range objects in python, but also accept tuples as input if no bounds information is necessary. The default is lower bound included, upper bound excluded.

### IntegerRangeField

class `IntegerRangeField`(**options)

  Stores a range of integers. Based on an `IntegerField`. Represented by an `int4range` in the database and a `NumericRange` in Python.

### BigIntegerRangeField

class `BigIntegerRangeField`(**options)

  Stores a range of large integers. Based on a `BigIntegerField`. Represented by an `int8range` in the database and a `NumericRange` in Python.

### FloatRangeField

class `FloatRangeField`(**options)

  Stores a range of floating point values. Based on a `FloatField`. Represented by a `numrange` in the database and a `NumericRange` in Python.

### DateTimeRangeField

class `DateTimeRangeField`(**options)

  Stores a range of timestamps. Based on a `DateTimeField`. Represented by a `tztsrange` in the database and a `DateTimeTZRange` in Python.

### DateRangeField

class `DateRangeField`(**options)

  Stores a range of dates. Based on a `DateField`. Represented by a `daterange` in the database and a `DateRange` in Python.

### 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()

        def __str__(self):  # __unicode__ on Python 2
            return self.name

We will also use the following example objects:

    >>> Event.objects.create(name='Soft play', ages=(0, 10))
    >>> Event.objects.create(name='Pub trip', ages=(21, None))

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))
    [<Event: Soft play>]

##### contained_by

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

##### overlap

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

##### adjacent_to

The returned ranges share a bound with the passed range.

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

#### 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)
    [<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)
    [<Event: Soft play>]

##### isempty

Returned objects are empty ranges. Can be chained to valid lookups for a `BooleanField`.

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

#### 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 `register_range()` to allow use of custom range types.

class `RangeField`(**options)

  Base class for model range fields.

  `base_field`

    The model field to use.

  `range_type`

    The psycopg2 range type to use.

  `form_field`

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

class `django.contrib.postgres.forms.``BaseRangeField`

  Base class for form range fields.

  `base_field`

    The form field to use.

  `range_type`

    The psycopg2 range type to use.