Fixed #24997 -- Enabled bulk_create() on proxy models

    Wiktor Kołodziej <wiktor@pykonik.org>

    Wiley Kestner <wiley.kestner@gmail.com>

    Wiliam Alves de Souza <wiliamsouza83@gmail.com>

    William Schwartz <wkschwartz@gmail.com>

    Will Hardy <django@willhardy.com.au>

    Wilson Miner <wminer@gmail.com>

    wojtek

        Inserts each of the instances into the database. This does *not* call

        save() on each of the instances, does not send any pre/post save

        signals, and does not set the primary key attribute if it is an

        autoincrement field.

        autoincrement field. Multi-table models are not supported.

        """

        # So this case is fun. When you bulk insert you don't get the primary

        # keys back (if it's an autoincrement), so you can't insert into the

        # this by using RETURNING clause for the insert query. We're punting

        # on these for now because they are relatively rare cases.

        assert batch_size is None or batch_size > 0

        if self.model._meta.parents:

            raise ValueError("Can't bulk create an inherited model")

        # Check that the parents share the same concrete model with the our

        # model to detect the inheritance pattern ConcreteGrandParent ->

        # MultiTableParent -> ProxyChild. Simply checking self.model._meta.proxy

        # would not identify that case as involving multiple tables.

        for parent in self.model._meta.get_parent_list():

            if parent._meta.concrete_model is not self.model._meta.concrete_model:

                raise ValueError("Can't bulk create a multi-table inherited model")

        if not objs:

            return objs

        self._for_write = True

        connection = connections[self.db]

        fields = self.model._meta.local_concrete_fields

        fields = self.model._meta.concrete_fields

        objs = list(objs)

        self._populate_pk_values(objs)

        with transaction.atomic(using=self.db, savepoint=False):

  does not retrieve and set the primary key attribute, as ``save()`` does.

* It does not work with many-to-many relationships.

.. versionchanged:: 1.9

    Support for using ``bulk_create()`` with proxy models was added.

The ``batch_size`` parameter controls how many objects are created in single

query. The default is to create all objects in one batch, except for SQLite

where the default is such that at most 999 variables per query are used.

Models

^^^^^^

* :meth:`QuerySet.bulk_create() <django.db.models.query.QuerySet.bulk_create>`

  now works on proxy models.

* Database configuration gained a :setting:`TIME_ZONE <DATABASE-TIME_ZONE>`

  option for interacting with databases that store datetimes in local time and

  don't support time zones when :setting:`USE_TZ` is ``True``.

    iso_two_letter = models.CharField(max_length=2)

class ProxyCountry(Country):

    class Meta:

        proxy = True

class ProxyProxyCountry(ProxyCountry):

    class Meta:

        proxy = True

class ProxyMultiCountry(ProxyCountry):

    pass

class ProxyMultiProxyCountry(ProxyMultiCountry):

    class Meta:

        proxy = True

class Place(models.Model):

    name = models.CharField(max_length=100)