Remove automagic pk-based sequence setup

Related to issues #78, #92, #103, #111, #153, #170

The default value of all sequences is now 0; the automagic
``_setup_next_sequence`` behavior of Django/SQLAlchemy has been removed.

This feature's only goal was to allow the following scenario:

1. Run a Python script that uses MyFactory.create() a couple of times
   (with a unique field based on the sequence counter)
2. Run the same Python script a second time

Without the magical ``_setup_next_sequence``, the Sequence counter would be set
to 0 at the beginning of each script run, so both runs would generate objects
with the same values for the unique field ; thus conflicting and crashing.

The above behavior having only a very limited use and bringing various
issues (hitting the database on ``build()``, problems with non-integer
or composite primary key columns, ...), it has been removed.

It could still be emulated through custom ``_setup_next_sequence``
methods, or by calling ``MyFactory.reset_sequence()``.

2 files changed, 0 insertions, 27 deletions

diff --git a/factory/alchemy.py b/factory/alchemy.py
index 3c91411..2cd28bb 100644
--- a/factory/alchemy.py
+++ b/factory/alchemy.py
@@ -44,18 +44,6 @@ class SQLAlchemyModelFactory(base.Factory):
     })
 
     @classmethod
-    def _setup_next_sequence(cls, *args, **kwargs):
-        """Compute the next available PK, based on the 'pk' database field."""
-        session = cls._meta.sqlalchemy_session
-        model = cls._meta.model
-        pk = getattr(model, model.__mapper__.primary_key[0].name)
-        max_pk = session.query(max(pk)).one()[0]
-        if isinstance(max_pk, int):
-            return max_pk + 1 if max_pk else 1
-        else:
-            return 1
-
-    @classmethod
     def _create(cls, model_class, *args, **kwargs):
         """Create an instance of the model, and save it to the database."""
         session = cls._meta.sqlalchemy_session
diff --git a/factory/django.py b/factory/django.py
index 2b6c463..c58a6e2 100644
--- a/factory/django.py
+++ b/factory/django.py
@@ -110,21 +110,6 @@ class DjangoModelFactory(base.Factory):
             return model_class.objects
 
     @classmethod
-    def _setup_next_sequence(cls):
-        """Compute the next available PK, based on the 'pk' database field."""
-
-        model = cls._get_model_class()  # pylint: disable=E1101
-        manager = cls._get_manager(model)
-
-        try:
-            return 1 + manager.values_list('pk', flat=True
-                ).order_by('-pk')[0]
-        except (IndexError, TypeError):
-            # IndexError: No instance exist yet
-            # TypeError: pk isn't an integer type
-            return 1
-
-    @classmethod
     def _get_or_create(cls, model_class, *args, **kwargs):
         """Create an instance of the model through objects.get_or_create."""
         manager = cls._get_manager(model_class)