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Fixed #19756 - Corrected a ManyToMany example and added some links and markup.
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@ -35,7 +35,7 @@ objects, and a ``Publication`` has multiple ``Article`` objects:
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What follows are examples of operations that can be performed using the Python
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API facilities.
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Create a couple of Publications::
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Create a couple of ``Publications``::
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>>> p1 = Publication(title='The Python Journal')
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>>> p1.save()
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@ -44,11 +44,11 @@ Create a couple of Publications::
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>>> p3 = Publication(title='Science Weekly')
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>>> p3.save()
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Create an Article::
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Create an ``Article``::
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>>> a1 = Article(headline='Django lets you build Web apps easily')
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You can't associate it with a Publication until it's been saved::
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You can't associate it with a ``Publication`` until it's been saved::
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>>> a1.publications.add(p1)
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Traceback (most recent call last):
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@ -60,11 +60,11 @@ Save it!
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>>> a1.save()
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Associate the Article with a Publication::
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Associate the ``Article`` with a ``Publication``::
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>>> a1.publications.add(p1)
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Create another Article, and set it to appear in both Publications::
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Create another ``Article``, and set it to appear in both ``Publications``::
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>>> a2 = Article(headline='NASA uses Python')
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>>> a2.save()
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@ -75,25 +75,26 @@ Adding a second time is OK::
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>>> a2.publications.add(p3)
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Adding an object of the wrong type raises TypeError::
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Adding an object of the wrong type raises :exc:`~exceptions.TypeError`::
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>>> a2.publications.add(a1)
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Traceback (most recent call last):
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...
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TypeError: 'Publication' instance expected
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Add a Publication directly via publications.add by using keyword arguments::
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Create and add a ``Publication`` to an ``Article`` in one step using
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:meth:`~django.db.models.fields.related.RelatedManager.create`::
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>>> new_publication = a2.publications.create(title='Highlights for Children')
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Article objects have access to their related Publication objects::
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``Article`` objects have access to their related ``Publication`` objects::
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>>> a1.publications.all()
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[<Publication: The Python Journal>]
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>>> a2.publications.all()
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[<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]
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Publication objects have access to their related Article objects::
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``Publication`` objects have access to their related ``Article`` objects::
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>>> p2.article_set.all()
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[<Article: NASA uses Python>]
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@ -102,7 +103,8 @@ Publication objects have access to their related Article objects::
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>>> Publication.objects.get(id=4).article_set.all()
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[<Article: NASA uses Python>]
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Many-to-many relationships can be queried using :ref:`lookups across relationships <lookups-that-span-relationships>`::
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Many-to-many relationships can be queried using :ref:`lookups across
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relationships <lookups-that-span-relationships>`::
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>>> Article.objects.filter(publications__id__exact=1)
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[<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]
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@ -119,7 +121,8 @@ Many-to-many relationships can be queried using :ref:`lookups across relationshi
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>>> Article.objects.filter(publications__title__startswith="Science").distinct()
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[<Article: NASA uses Python>]
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The count() function respects distinct() as well::
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The :meth:`~django.db.models.query.QuerySet.count` function respects
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:meth:`~django.db.models.query.QuerySet.distinct` as well::
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>>> Article.objects.filter(publications__title__startswith="Science").count()
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2
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@ -133,7 +136,7 @@ The count() function respects distinct() as well::
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[<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]
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Reverse m2m queries are supported (i.e., starting at the table that doesn't have
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a ManyToManyField)::
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a :class:`~django.db.models.ManyToManyField`)::
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>>> Publication.objects.filter(id__exact=1)
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[<Publication: The Python Journal>]
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@ -163,7 +166,7 @@ involved is a little complex)::
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>>> Article.objects.exclude(publications=p2)
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[<Article: Django lets you build Web apps easily>]
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If we delete a Publication, its Articles won't be able to access it::
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If we delete a ``Publication``, its ``Articles`` won't be able to access it::
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>>> p1.delete()
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>>> Publication.objects.all()
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@ -172,7 +175,7 @@ If we delete a Publication, its Articles won't be able to access it::
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>>> a1.publications.all()
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[]
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If we delete an Article, its Publications won't be able to access it::
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If we delete an ``Article``, its ``Publications`` won't be able to access it::
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>>> a2.delete()
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>>> Article.objects.all()
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@ -199,7 +202,7 @@ Adding via the other end using keywords::
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>>> a5.publications.all()
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[<Publication: Science News>]
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Removing publication from an article::
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Removing ``Publication`` from an ``Article``::
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>>> a4.publications.remove(p2)
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>>> p2.article_set.all()
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@ -242,7 +245,7 @@ And you can clear from the other end::
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>>> p2.article_set.all()
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[<Article: Oxygen-free diet works wonders>]
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Recreate the article and Publication we have deleted::
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Recreate the ``Article`` and ``Publication`` we have deleted::
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>>> p1 = Publication(title='The Python Journal')
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>>> p1.save()
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@ -250,7 +253,8 @@ Recreate the article and Publication we have deleted::
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>>> a2.save()
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>>> a2.publications.add(p1, p2, p3)
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Bulk delete some Publications - references to deleted publications should go::
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Bulk delete some ``Publications`` - references to deleted publications should
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go::
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>>> Publication.objects.filter(title__startswith='Science').delete()
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>>> Publication.objects.all()
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@ -267,15 +271,18 @@ Bulk delete some articles - references to deleted objects should go::
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[<Article: Django lets you build Web apps easily>]
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>>> q.delete()
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After the delete, the QuerySet cache needs to be cleared, and the referenced
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objects should be gone::
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After the :meth:`~django.db.models.query.QuerySet.delete`, the
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:class:`~django.db.models.query.QuerySet` cache needs to be cleared, and the
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referenced objects should be gone::
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>>> print(q)
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[]
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>>> p1.article_set.all()
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[<Article: NASA uses Python>]
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An alternate to calling clear() is to assign the empty set::
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An alternate to calling
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:meth:`~django.db.models.fields.related.RelatedManager.clear` is to assign the
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empty set::
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>>> p1.article_set = []
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>>> p1.article_set.all()
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