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PostgreSQL 特有查询表达式Link to this heading#

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这些表达式可以从 django.contrib.postgres.expressions 模块中获得。

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ArraySubquery() 表达式Link to this heading#

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\nclass ArraySubquery(queryset)Link to this definition#
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ArraySubquery 是一个 Subquery，使用 PostgreSQL 的 ARRAY 构造函数，从查询集中建立一个值列表，它必须使用 QuerySet.values() 来只返回一个列。

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这个类与 ArrayAgg 不同，它不作为一个聚合函数，也不需要一个 SQL GROUP BY 子句来建立值的列表。

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例如，如果您想要将作者的所有相关书籍注释为 JSON 对象：

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Python console
>>> from django.db.models import OuterRef\n>>> from django.db.models.functions import JSONObject\n>>> from django.contrib.postgres.expressions import ArraySubquery\n>>> books = Book.objects.filter(author=OuterRef("pk")).values(\n...     json=JSONObject(title="title", pages="pages")\n... )\n>>> author = Author.objects.annotate(books=ArraySubquery(books)).first()\n>>> author.books\n[{'title': 'Solaris', 'pages': 204}, {'title': 'The Cyberiad', 'pages': 295}]\n
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