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Code Issues 32 Releases Wiki Activity

Fixed #17003 - prefetch_related should support foreign keys/one-to-one

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Support for `GenericForeignKey` is also included.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16939 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Luke Plant
2011-10-07 16:05:53 +00:00
parent 672f2db24a
commit 052a011ee6
8 changed files with 366 additions and 119 deletions
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docs/releases/1.4.txt
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@@ -66,15 +66,18 @@ information.
``QuerySet.prefetch_related``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Analagous to :meth:`~django.db.models.query.QuerySet.select_related` but for
many-to-many relationships,
Similar to :meth:`~django.db.models.query.QuerySet.select_related` but with a
different strategy and broader scope,
:meth:`~django.db.models.query.QuerySet.prefetch_related` has been added to
:class:`~django.db.models.query.QuerySet`. This method returns a new ``QuerySet``
that will prefetch in a single batch each of the specified related lookups as
soon as it begins to be evaluated (e.g. by iterating over it). This enables you
to fix many instances of a very common performance problem, in which your code
ends up doing O(n) database queries (or worse) if objects on your primary
``QuerySet`` each have many related objects that you also need.
:class:`~django.db.models.query.QuerySet`. This method returns a new
``QuerySet`` that will prefetch in a single batch each of the specified related
lookups as soon as it begins to be evaluated. Unlike ``select_related``, it does
the joins in Python, not in the database, and supports many-to-many
relationships, :class:`~django.contrib.contenttypes.generic.GenericForeignKey`
and more. This enables you to fix many instances of a very common performance
problem, in which your code ends up doing O(n) database queries (or worse) if
objects on your primary ``QuerySet`` each have many related objects that you
also need.
HTML5
~~~~~