sqla_polymorphism_boolean_example.py

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()


class Item(Base):
    __tablename__ = "item"
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.VARCHAR(128))
    status = sa.Column(
        sa.Enum("DRAFT", "PUBLISHED"), default="DRAFT", server_default=sa.text("'DRAFT'"), nullable=False,
    )


class DraftItem(Item):
    __mapper_args__ = {
        "polymorphic_on": "status",
        "polymorphic_identity": "DRAFT",
    }


class PublishedItem(Item):
    __mapper_args__ = {
        "polymorphic_on": "status",
        "polymorphic_identity": "PUBLISHED",
    }


engine = sa.create_engine("sqlite:///:memory:", echo=False)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()


draft_item = DraftItem(name="draft-1")
published_item = PublishedItem(name="published-1")
session.add(published_item)
session.add(draft_item)
session.commit()

print("\nDraft Items")
print("====================")
for f in session.query(DraftItem):
    print(f.name, f.status, f.id)

print("\nPublished Items")
print("====================")
for f in session.query(PublishedItem):
    print(f.name, f.status, f.id)

print("\nAll Items")
print("====================")
for f in session.query(Item):
    print(f.name, f.status, f.id)