查看“Django/docs/3.0.x/ref/contrib/postgres/functions”的源代码

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= PostgreSQL specific database functions =

All of these functions are available from the
<code>django.contrib.postgres.functions</code> module.

<div id="randomuuid" class="section">

== <code>RandomUUID</code> ==

; ''class'' <code>RandomUUID</code>
: 

Returns a version 4 UUID.

The [https://www.postgresql.org/docs/current/pgcrypto.html pgcrypto extension] must be installed. You can use the
[[../operations#django.contrib.postgres.operations|<code>CryptoExtension</code>]] migration
operation to install it.

使用实例：

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<pre>&gt;&gt;&gt; from django.contrib.postgres.functions import RandomUUID
&gt;&gt;&gt; Article.objects.update(uuid=RandomUUID())</pre>

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<div id="transactionnow" class="section">

== <code>TransactionNow</code> ==

; ''class'' <code>TransactionNow</code>
: 

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
[[../../../models/database-functions#django.db.models.functions|<code>django.db.models.functions.Now</code>]], which returns the date and time of the
current statement.

Note that only the outermost call to [[../../../../topics/db/transactions#django.db.transaction|<code>atomic()</code>]]
sets up a transaction and thus sets the time that <code>TransactionNow()</code> will
return; nested calls create savepoints which do not affect the transaction
time.

使用实例：

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<pre>&gt;&gt;&gt; from django.contrib.postgres.functions import TransactionNow
&gt;&gt;&gt; Article.objects.filter(published__lte=TransactionNow())
&lt;QuerySet [&lt;Article: How to Django&gt;]&gt;</pre>

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