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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>]>
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