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PostgreSQL specific database functions

======================================

All of these functions are available from the

``django.contrib.postgres.functions`` module.

.. currentmodule:: django.contrib.postgres.functions

``RandomUUID``

==============

.. class:: RandomUUID()

Returns a version 4 UUID.

On PostgreSQL < 13, the `pgcrypto extension`_ must be installed. You can use

the :class:`~django.contrib.postgres.operations.CryptoExtension` migration

operation to install it.

.. _pgcrypto extension: https://www.postgresql.org/docs/current/pgcrypto.html

Usage example::

    >>> from django.contrib.postgres.functions import RandomUUID

    >>> Article.objects.update(uuid=RandomUUID())

``TransactionNow``

==================

.. class:: TransactionNow()

Returns the date and time on the database server that the current transaction

started. If you are not in a transaction it will return the date and time of

the current statement. This is a complement to

:class:`django.db.models.functions.Now`, which returns the date and time of the

current statement.

Note that only the outermost call to :func:`~django.db.transaction.atomic()`

sets up a transaction and thus sets the time that ``TransactionNow()`` will

return; nested calls create savepoints which do not affect the transaction

time.

Usage example::

    >>> from django.contrib.postgres.functions import TransactionNow

    >>> Article.objects.filter(published__lte=TransactionNow())

    <QuerySet [<Article: How to Django>]>