Commit ea9a0857 authored by Selwin Ong's avatar Selwin Ong Committed by Anssi Kääriäinen
Browse files

Fixed #19326 -- Added first() and last() methods to QuerySet

parent d595b61a

django/db/models/manager.py

+6 −0
Original line number Diff line number Diff line
@@ -186,6 +186,12 @@ class Manager(six.with_metaclass(RenameManagerMethods)): 
    def latest(self, *args, **kwargs):

        return self.get_queryset().latest(*args, **kwargs)



    def first(self):

        return self.get_queryset().first()



    def last(self):

        return self.get_queryset().last()



    def order_by(self, *args, **kwargs):

        return self.get_queryset().order_by(*args, **kwargs)

django/db/models/query.py

+20 −0
Original line number Diff line number Diff line
@@ -498,6 +498,26 @@ class QuerySet(object): 
    def latest(self, field_name=None):

        return self._earliest_or_latest(field_name=field_name, direction="-")



    def first(self):

        """

        Returns the first object of a query, returns None if no match is found.

        """

        qs = self if self.ordered else self.order_by('pk')

        try:

            return qs[0]

        except IndexError:

            return None



    def last(self):

        """

        Returns the last object of a query, returns None if no match is found.

        """

        qs = self.reverse() if self.ordered else self.order_by('-pk')

        try:

            return qs[0]

        except IndexError:

            return None



    def in_bulk(self, id_list):

        """

        Returns a dictionary mapping each of the given IDs to the object with

docs/ref/models/querysets.txt

+30 −0
Original line number Diff line number Diff line
@@ -1585,6 +1585,36 @@ earliest 
Works otherwise like :meth:`~django.db.models.query.QuerySet.latest` except

the direction is changed.



first

~~~~~

.. method:: first()



.. versionadded:: 1.6



Returns the first object matched by the queryset, or ``None`` if there

is no matching object. If the ``QuerySet`` has no ordering defined, then the

queryset is automatically ordered by the primary key.



Example::



    p = Article.objects.order_by('title', 'pub_date').first()



Note that ``first()`` is a convenience method, the following code sample is

equivalent to the above example::



    try:

        p = Article.objects.order_by('title', 'pub_date')[0]

    except IndexError:

        p = None



last

~~~~

.. method:: last()



.. versionadded:: 1.6



Works like  :meth:`first()` except the ordering is reversed.



aggregate

~~~~~~~~~

docs/releases/1.6.txt

+5 −0
Original line number Diff line number Diff line
@@ -253,6 +253,11 @@ Minor features 
  allow users to specify the primary keys of objects they want to dump.

  This option can only be used with one model.



* Added ``QuerySet`` methods :meth:`~django.db.models.query.QuerySet.first`

  and :meth:`~django.db.models.query.QuerySet.last` which are convenience

  methods returning the first or last object matching the filters. Returns

  ``None`` if there are no objects matching.



Backwards incompatible changes in 1.6

=====================================

tests/get_earliest_or_latest/tests.py

+31 −0
Original line number Diff line number Diff line
@@ -121,3 +121,34 @@ class EarliestOrLatestTests(TestCase): 
        p2 = Person.objects.create(name="Stephanie", birthday=datetime(1960, 2, 3))

        self.assertRaises(AssertionError, Person.objects.latest)

        self.assertEqual(Person.objects.latest("birthday"), p2)



    def test_first(self):

        p1 = Person.objects.create(name="Bob", birthday=datetime(1950, 1, 1))

        p2 = Person.objects.create(name="Alice", birthday=datetime(1961, 2, 3))

        self.assertEqual(

            Person.objects.first(), p1)

        self.assertEqual(

            Person.objects.order_by('name').first(), p2)

        self.assertEqual(

            Person.objects.filter(birthday__lte=datetime(1955, 1, 1)).first(),

            p1)

        self.assertIs(

            Person.objects.filter(birthday__lte=datetime(1940, 1, 1)).first(),

            None)



    def test_last(self):

        p1 = Person.objects.create(

            name="Alice", birthday=datetime(1950, 1, 1))

        p2 = Person.objects.create(

            name="Bob", birthday=datetime(1960, 2, 3))

        # Note: by default PK ordering.

        self.assertEqual(

            Person.objects.last(), p2)

        self.assertEqual(

            Person.objects.order_by('-name').last(), p1)

        self.assertEqual(

            Person.objects.filter(birthday__lte=datetime(1955, 1, 1)).last(),

            p1)

        self.assertIs(

            Person.objects.filter(birthday__lte=datetime(1940, 1, 1)).last(),

            None)