{"title":"PostgreSQL 固有のクエリ式","version":"6.1","locale":"ja","docname":"ref/contrib/postgres/expressions","url":"/ja/6.1/ref/contrib/postgres/expressions/","canonical":"https://djangodocs.dev/ja/6.1/ref/contrib/postgres/expressions/","summary":"これらの式は django.contrib.postgres.expressions モジュールから利用できます。 ArraySubquery() 式 Link to this heading # class ArraySubquery ( queryset ) Link to this definition #…","html":"

PostgreSQL 固有のクエリ式Link to this heading#

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これらの式は django.contrib.postgres.expressions モジュールから利用できます。

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ArraySubquery() 式Link to this heading#

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\nclass ArraySubquery(queryset)Link to this definition#
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ArraySubquery は、PostgreSQL の ARRAY コンストラクタを使用してクエリセットから値のリストを構築する Subquery です。クエリセットは QuerySet.values() を使用して、1つの列のみを返す必要があります。

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このクラスは、ArrayAgg と異なり、集計関数として機能せず、値のリストを構築する際にSQLの GROUP BY 句を必要としません。

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例えば、特定の著者に関連する全ての書籍を JSON オブジェクトとしてアノテーションしたい場合は、次のようにします:

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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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