From 68bd8f4cb4d14dccfb016bb15177506234f567fb Mon Sep 17 00:00:00 2001 From: Ryan Cheley Date: Sun, 30 Oct 2022 09:43:21 -0700 Subject: [PATCH] Fixed #24048 -- Corrected QuerySet.only() docs about interaction with defer(). --- docs/ref/models/querysets.txt | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt index 671acd3026..57c64e32cf 100644 --- a/docs/ref/models/querysets.txt +++ b/docs/ref/models/querysets.txt @@ -1707,9 +1707,11 @@ one, doing so will result in an error. .. method:: only(*fields) -The ``only()`` method is more or less the opposite of :meth:`defer()`. You call -it with the fields that should *not* be deferred when retrieving a model. If -you have a model where almost all the fields need to be deferred, using +The ``only()`` method is essentially the opposite of :meth:`defer`. Only the +fields passed into this method and that are *not* already specified as deferred +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 code. @@ -1734,8 +1736,7 @@ logically:: # Final result is that everything except "headline" is deferred. Entry.objects.only("headline", "body").defer("body") - # Final result loads headline and body immediately (only() replaces any - # existing set of fields). + # Final result loads headline immediately. Entry.objects.defer("body").only("headline", "body") 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 :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()`` ~~~~~~~~~~~