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Fixed #24048 -- Corrected QuerySet.only() docs about interaction with defer().

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Ryan Cheley 2022-10-30 09:43:21 -07:00 committed by Mariusz Felisiak
parent 514884e9a5
commit 68bd8f4cb4
1 changed files with 11 additions and 5 deletions
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16
docs/ref/models/querysets.txt
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@ -1707,9 +1707,11 @@ one, doing so will result in an error.
.. method:: only(*fields) .. method:: only(*fields)
The ``only()`` method is more or less the opposite of :meth:`defer()`. You call The ``only()`` method is essentially the opposite of :meth:`defer`. Only the
it with the fields that should *not* be deferred when retrieving a model. If fields passed into this method and that are *not* already specified as deferred
you have a model where almost all the fields need to be deferred, using are loaded immediately when the queryset is evaluated.
If you have a model where almost all the fields need to be deferred, using
``only()`` to specify the complementary set of fields can result in simpler ``only()`` to specify the complementary set of fields can result in simpler
code. code.
@ -1734,8 +1736,7 @@ logically::
# Final result is that everything except "headline" is deferred. # Final result is that everything except "headline" is deferred.
Entry.objects.only("headline", "body").defer("body") Entry.objects.only("headline", "body").defer("body")
# Final result loads headline and body immediately (only() replaces any # Final result loads headline immediately.
# existing set of fields).
Entry.objects.defer("body").only("headline", "body") Entry.objects.defer("body").only("headline", "body")
All of the cautions in the note for the :meth:`defer` documentation apply to All of the cautions in the note for the :meth:`defer` documentation apply to
@ -1756,6 +1757,11 @@ are in your ``only()`` call.
deferred fields, only the loaded fields will be saved. See deferred fields, only the loaded fields will be saved. See
:meth:`~django.db.models.Model.save()` for more details. :meth:`~django.db.models.Model.save()` for more details.
.. note::
When using :meth:`defer` after ``only()`` the fields in :meth:`defer` will
override ``only()`` for fields that are listed in both.
``using()`` ``using()``
~~~~~~~~~~~ ~~~~~~~~~~~