[Sqlalchemy-tickets] Issue #4026: mixing selectin load on top of inline (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 4026: mixing selectin load on top of inline
https://bitbucket.org/zzzeek/sqlalchemy/issues/4026/mixing-selectin-load-on-top-of-inline

Michael Bayer:

pushing the new feature beyond what was planned see how hard this would be


```
#!python

from sqlalchemy import Table, Column, Integer, String, ForeignKey, create_engine
from sqlalchemy.orm import Session
from sqlalchemy.ext.declarative import declarative_base


Base = declarative_base()


class Person(Base):
    __tablename__ = 'person'

    id = Column(Integer, primary_key=True)
    type = Column(String(50), nullable=False)
    name = Column(String(50))

    __mapper_args__ = {
        'polymorphic_identity': 'person',
        'polymorphic_on': type
    }


class Manager(Person):
    __tablename__ = 'manager'

    id = Column(ForeignKey('person.id'), primary_key=True)
    manager_name = Column(String(30))

    __mapper_args__ = {
        'polymorphic_identity': 'manager',
        'polymorphic_load': 'selectin'
    }


class EngineerBase(Person):
    __tablename__ = 'engineer'

    id = Column(ForeignKey('person.id'), primary_key=True)
    engineer_name = Column(String(30))

    __mapper_args__ = {
        'polymorphic_load': 'selectin'
    }


class EngineerType1(EngineerBase):
    __mapper_args__ = {
        'polymorphic_identity': 'engineer_t1',
        'polymorphic_load': 'inline'
    }


class EngineerType2(EngineerBase):
    __mapper_args__ = {
        'polymorphic_identity': 'engineer_t2',
        'polymorphic_load': 'inline'
    }


engine = create_engine('sqlite://', echo=True)
Base.metadata.create_all(engine)

engine.echo = True

session = Session(engine)

eng1 = EngineerType1()
eng2 = EngineerType2()

session.add_all([eng1, eng2])
session.commit()

session.query(Person).all()
```