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Nathanna fiosrúcháin sonracha PostgreSQLLink to this heading#

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Tá na nathanna seo ar fáil ón modúl django.contrib.postgres.expressions.

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Nathanna ``ArraySubquery () ``Link to this heading#

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\nclass ArraySubquery(queryset)Link to this definition#
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Is é ArraySubquery a:class: ~django.db.models.subquery a úsáideann an tógálaí PostgreSQL ARRAY chun liosta luachanna a thógáil ón gceist, nach mór a úsáid:meth: .queryset.values chun ach colún amháin a thabhairt ar ais.

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Tá difríocht idir an rang seo ó:class: ~django.contrib.postgres.aggregates.ArrayAgg sa chaoi nach ngníomhaíonn sé mar fheidhm chomhiomlán agus nach dteastaíonn clásal SQL GROUP BY uaidh chun an liosta luachanna a thógáil.

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Mar shampla, más mian leat gach leabhar gaolmhar a anótáil le húdar mar rudaí JSON:

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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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