Hello All,
I'm trying to use the new bulk_save_objects() to improve performance on
bulk inserts, and have run into a problem. If bulk_save_objects() is used
to save objects of a polymorphic class..
1. They are created correctly in the DB, with polymorphic type column
populated correctly
2. BUT queries for the new objects will return one of incorrect type.
In my case I'm getting instances of Child1 back when I would expect to get
a Child2.
The following code demonstrates the problem:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, SmallInteger, String, ForeignKey
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Entity(Base):
__tablename__ = 'Entity'
Id = Column(Integer, primary_key=True, nullable=False)
Content = Column(String)
_polytype = Column(SmallInteger, nullable=False)
__mapper_args__ = {
'polymorphic_identity':1,
'polymorphic_on':_polytype
}
class Child1(Entity):
__tablename__ = 'Child1'
MyId = Column(ForeignKey("Entity.Id"), primary_key=True)
__mapper_args__ = {'polymorphic_identity':11}
class Child2(Entity):
__tablename__ = 'Child2'
MyId = Column(ForeignKey("Entity.Id"), primary_key=True)
__mapper_args__ = {'polymorphic_identity':12}
if __name__ == '__main__':
# engine = create_engine('sqlite:///:memory:', echo=False)
engine = create_engine('sqlite:///test.db', echo=False)
Session = sessionmaker(bind=engine)
sess = Session()
Base.metadata.create_all(engine)
c1_many = [Child1(Content="c1inst_%d"%i) for i in range(0,1000)]
c2_many = [Child2(Content="c2inst_%d"%i) for i in range(0,1000)]
sess.bulk_save_objects(c1_many)
sess.bulk_save_objects(c2_many)
# sess.add_all(c1_many)
# sess.add_all(c2_many)
sess.flush()
sess.commit()
for c in sess.query(Child1):
assert isinstance(c, Child1)
for c in sess.query(Child2):
assert isinstance(c, Child2)
All the calls to assert isinstance(c, Child1) complete successfully. But
once we start checking for Child2 - boom, we are still getting back Child1
instances.
At first I wondered if I was misunderstanding SA's implementation of
polymorphism, so tried inserting rows the traditional way with
sess.add_all(). But that works fine so I think I've exposed a bug in the
new bulk_save_objects() code.
My environment is Python 3.5.1, SQLAlchemy==1.0.12, SQLite 3.8.10.2 on OSX.
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