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Code Issues 32 Releases Wiki Activity

Fixed #16937 - added QuerySet.prefetch_related to prefetch many related objects.

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Many thanks to akaariai for lots of review and feedback, bug finding,
additional unit tests and performance testing.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16930 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Luke Plant
2011-10-05 23:14:52 +00:00
parent d30fbf8b78
commit 662eea116f
10 changed files with 968 additions and 24 deletions
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13
docs/releases/1.4.txt
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@@ -63,6 +63,19 @@ setup for test suites) has seen a performance benefit as a result.
See the :meth:`~django.db.models.query.QuerySet.bulk_create` docs for more
information.
``QuerySet.prefetch_related``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Analagous to :meth:`~django.db.models.query.QuerySet.select_related` but for
many-to-many relationships,
: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.
HTML5
~~~~~