Fix bulk create not working with multi-database setup

[ashiazed]

Bulk create now optionally uses the right DB when _using is defined.
#210

Using a combination of bulk_create and using requires some consideration by the user.
Django normally requires that two related objects are using the same DB, in a default router it can just check the state of each instance dynamically, but with bulk_create like this, that's not possible. This isn't a model bakery limitation.
I added tests to show the expected ValueError Django would return and a custom router that shows a successful bake.
Not sure if you want me to drop any other comments or docs to make sure this is clear.

Also fixed a copy/pasted typo in the test names for this test class, I can split it up into a different PR if needed,

[timjklein36]

This looks to me like a sensible way to handle this case. Thanks for the contribution!

[timjklein36]

Add newline between conditional blocks and return statement (for clarity).

[timjklein36]

Extra unneeded "and":

Suggested change

	def test_related_fk_database_specified_via_using_kwarg_combined_with_and_bulk_create(
	def test_related_fk_database_specified_via_using_kwarg_combined_with_bulk_create(

[timjklein36]

Great test setup. I like the simplicity of using override_settings as a context manager here.

[timjklein36]

I think a comment here would be useful. Something along these lines:

Suggested change

	manager = baker.model._base_manager.using(baker._using)
	# Try to use the desired DB and let Django fail if spanning
	# relationships without the proper router setup
	manager = baker.model._base_manager.using(baker._using)

But the test case you added helps to alleviate any confusion here.

[timjklein36]

Looks like some CI test failures and a missing CHANGELOG entry.

I will try to look into the test failures when I get a chance.

[timjklein36]

I am getting a consistent failure when running tests with PostgreSQL: TestBakerCreatesAssociatedModels.test_create_many_to_many_if_flagged.

The actual failure is rather cryptic:

______________________________________________________________________ TestBakerCreatesAssociatedModels.test_create_many_to_many_if_flagged _______________________________________________________________________
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/backends/utils.py:84: in _execute
    return self.cursor.execute(sql, params)
E   psycopg2.errors.InFailedSqlTransaction: current transaction is aborted, commands ignored until end of transaction block

The above exception was the direct cause of the following exception:
tests/test_baker.py:394: in test_create_many_to_many_if_flagged
    store = baker.make(models.Store, make_m2m=True)
model_bakery/baker.py:99: in make
    _save_kwargs=_save_kwargs, _refresh_after_create=_refresh_after_create, **attrs
model_bakery/baker.py:324: in make
    return self._make(**params)
model_bakery/baker.py:358: in _make
    self.m2m_dict[field.name] = self.m2m_value(field)
model_bakery/baker.py:404: in m2m_value
    return self.generate_value(field)
model_bakery/baker.py:594: in generate_value
    return generator(**generator_attrs)
model_bakery/random_gen.py:258: in gen_m2m
    return make(model, _quantity=MAX_MANY_QUANTITY, **attrs)
model_bakery/baker.py:95: in make
    for _ in range(_quantity)
model_bakery/baker.py:95: in <listcomp>
    for _ in range(_quantity)
model_bakery/baker.py:324: in make
    return self._make(**params)
model_bakery/baker.py:388: in _make
    _save_kwargs=_save_kwargs,
model_bakery/baker.py:418: in instance
    instance.save(**_save_kwargs)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/base.py:727: in save
    force_update=force_update, update_fields=update_fields)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/base.py:765: in save_base
    force_update, using, update_fields,
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/base.py:868: in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/base.py:908: in _do_insert
    using=using, raw=raw,
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/manager.py:85: in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/query.py:1270: in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/sql/compiler.py:1416: in execute_sql
    cursor.execute(sql, params)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/backends/utils.py:66: in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/backends/utils.py:75: in _execute_with_wrappers
    return executor(sql, params, many, context)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/backends/utils.py:84: in _execute
    return self.cursor.execute(sql, params)
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/utils.py:90: in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/backends/utils.py:84: in _execute
    return self.cursor.execute(sql, params)
E   django.db.utils.InternalError: current transaction is aborted, commands ignored until end of transaction block
---------------------------------------------------------------------------------------------- Captured stderr call -----------------------------------------------------------------------------------------------
Exception ignored in: <generator object cursor_iter at 0x7f4fdcbdd5d0>
Traceback (most recent call last):
  File "/home/tim/projects/model_bakery/.tox/py37-django32-postgresql/lib/python3.7/site-packages/django/db/models/sql/compiler.py", line 1649, in cursor_iter
    cursor.close()
psycopg2.errors.InvalidCursorName: cursor "_django_curs_139981442959168_sync_1" does not exist

This does not occur when running against SQLite.

[ashiazed]

iiinteresting. I'll spin up postgresql in docker and investigate. Cryptic indeed.

[ashiazed]

@timjklein36 that was such a sneaky failure, I had to move the _save_kwargs in bulk_create outside of the recursive function. I don't entirely know why but it was causing cascading transaction failures.

[berinhard]

Thanks @ashiazed for such an hacky PR =) =) =)

I know the flying kwargs can be a pain to figure out how they work, but thanks for trying and fixing them!