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53 lines
1.5 KiB
Plaintext
53 lines
1.5 KiB
Plaintext
======================================
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PostgreSQL specific database functions
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======================================
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All of these functions are available from the
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``django.contrib.postgres.functions`` module.
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.. currentmodule:: django.contrib.postgres.functions
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``RandomUUID``
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==============
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.. class:: RandomUUID()
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Returns a version 4 UUID.
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On PostgreSQL < 13, the `pgcrypto extension`_ must be installed. You can use
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the :class:`~django.contrib.postgres.operations.CryptoExtension` migration
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operation to install it.
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.. _pgcrypto extension: https://www.postgresql.org/docs/current/pgcrypto.html
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Usage example:
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.. code-block:: pycon
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>>> from django.contrib.postgres.functions import RandomUUID
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>>> Article.objects.update(uuid=RandomUUID())
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``TransactionNow``
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==================
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.. class:: TransactionNow()
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Returns the date and time on the database server that the current transaction
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started. If you are not in a transaction it will return the date and time of
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the current statement. This is a complement to
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:class:`django.db.models.functions.Now`, which returns the date and time of the
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current statement.
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Note that only the outermost call to :func:`~django.db.transaction.atomic()`
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sets up a transaction and thus sets the time that ``TransactionNow()`` will
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return; nested calls create savepoints which do not affect the transaction
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time.
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Usage example:
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.. code-block:: pycon
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>>> from django.contrib.postgres.functions import TransactionNow
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>>> Article.objects.filter(published__lte=TransactionNow())
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<QuerySet [<Article: How to Django>]>
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