Fixed #23732 -- Corrected and enhanced select_related() docs.

    # in the previous query.

    b = e.blog

You can use ``select_related()`` with any queryset of objects::

    from django.utils import timezone

    # Find all the blogs with entries scheduled to be published in the future.

    blogs = set()

    for e in Entry.objects.filter(pub_date__gt=timezone.now()).select_related('blog'):

        # Without select_related(), this would make a database query for each

        # loop iteration in order to fetch the related blog for each entry.

        blogs.add(e.blog)

The order of ``filter()`` and ``select_related()`` chaining isn't important.

These querysets are equivalent::

    Entry.objects.filter(pub_date__gt=timezone.now()).selected_related('blog')

    Entry.objects.selected_related('blog').filter(pub_date__gt=timezone.now())

You can follow foreign keys in a similar way to querying them. If you have the

following models::

        # ...

        author = models.ForeignKey(Person)

... then a call to ``Book.objects.select_related('person__city').get(id=4)``

... then a call to ``Book.objects.select_related('author__hometown').get(id=4)``

will cache the related ``Person`` *and* the related ``City``::

    b = Book.objects.select_related('person__city').get(id=4)

    b = Book.objects.select_related('author__hometown').get(id=4)

    p = b.author         # Doesn't hit the database.

    c = p.hometown       # Doesn't hit the database.