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.. include:: ./snippets/postgres_doc_links.rst
.. include:: ./snippets/manager_model_warning.rst
.. _hstore_page:
HStore
======
:class:`psqlextra.fields.HStoreField` is based on Django's :class:`~django:django.contrib.postgres.fields.HStoreField` and therefore supports everything Django does natively and more.
Constraints
-----------
Unique
******
The ``uniqueness`` constraint can be added on one or more `hstore`_ keys, similar to how a ``UNIQUE`` constraint can be added to a column. Setting this option causes unique indexes to be created on the specified keys.
You can specify a ``list`` of strings to specify the keys that must be marked as unique:
.. code-block:: python
from psqlextra.fields import HStoreField
from psqlextra.models import PostgresModel
class MyModel(PostgresModel):
myfield = HStoreField(uniqueness=['key1']
MyModel.objects.create(myfield={'key1': 'value1'})
MyModel.objects.create(myfield={'key1': 'value1'})
The second :meth:`~django:django.db.models.query.QuerySet.create` call will fail with a :class:`~django:django.db.IntegrityError` because there's already a row with ``key1=value1``.
Uniqueness can also be enforced "together", similar to Django's :attr:`~django:django.db.models.Options.unique_together` by specifying a tuple of fields rather than a single string:
.. code-block:: python
myfield = HStoreField(uniqueness=[('key1', 'key2'), 'key3'])
In the example above, ``key1`` and ``key2`` must unique **together**, and ``key3`` must unique on its own. By default, none of the keys are marked as "unique".
Required
********
The ``required`` option can be added to ensure that the specified `hstore`_ keys are set for every row. This is similar to a ``NOT NULL`` constraint on a column. You can specify a list of `hstore`_ keys that are required:
.. code-block:: python
from psqlextra.fields import HStoreField
from psqlextra.models import PostgresModel
class MyModel(PostgresModel):
myfield = HStoreField(required=['key1'])
mymodel.objects.create(myfield={'key1': none})
MyModel.objects.create(myfield={'key2': 'value1'})
Both calls to :meth:`~django:django.db.models.query.QuerySet.create` would fail in the example above since they do not provide a non-null value for ``key1``. By default, none of the keys are required.
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