examples.dogpile_caching.model — SQLAlchemy 2.0 Documentation

Release: 2.0.48 | Release Date: March 2, 2026

# SQLAlchemy 2.0 Documentation

# Source code for examples.dogpile_caching.model

    """The datamodel, which represents Person that has multiple
    Address objects, each with PostalCode, City, Country.

    Person --(1..n)--> Address
    Address --(has a)--> PostalCode
    PostalCode --(has a)--> City
    City --(has a)--> Country

    """

    from sqlalchemy import Column
    from sqlalchemy import ForeignKey
    from sqlalchemy import Integer
    from sqlalchemy import String
    from sqlalchemy.orm import relationship
    from .caching_query import RelationshipCache
    from .environment import Base
    from .environment import bootstrap

    class Country(Base):
        __tablename__ = "country"

        id = Column(Integer, primary_key=True)
        name = Column(String(100), nullable=False)

        def __init__(self, name):
            self.name = name

    class City(Base):
        __tablename__ = "city"

        id = Column(Integer, primary_key=True)
        name = Column(String(100), nullable=False)
        country_id = Column(Integer, ForeignKey("country.id"), nullable=False)
        country = relationship(Country)

        def __init__(self, name, country):
            self.name = name
            self.country = country

    class PostalCode(Base):
        __tablename__ = "postal_code"

        id = Column(Integer, primary_key=True)
        code = Column(String(10), nullable=False)
        city_id = Column(Integer, ForeignKey("city.id"), nullable=False)
        city = relationship(City)

        @property
        def country(self):
            return self.city.country

        def __init__(self, code, city):
            self.code = code
            self.city = city

    class Address(Base):
        __tablename__ = "address"

        id = Column(Integer, primary_key=True)
        person_id = Column(Integer, ForeignKey("person.id"), nullable=False)
        street = Column(String(200), nullable=False)
        postal_code_id = Column(Integer, ForeignKey("postal_code.id"))
        postal_code = relationship(PostalCode)

        @property
        def city(self):
            return self.postal_code.city

        @property
        def country(self):
            return self.postal_code.country

        def __str__(self):
            return "%s\t%s, %s\t%s" % (
                self.street,
                self.city.name,
                self.postal_code.code,
                self.country.name,
            )

    class Person(Base):
        __tablename__ = "person"

        id = Column(Integer, primary_key=True)
        name = Column(String(100), nullable=False)
        addresses = relationship(Address, collection_class=set)

        def __init__(self, name, *addresses):
            self.name = name
            self.addresses = set(addresses)

        def __str__(self):
            return self.name

        def __repr__(self):
            return "Person(name=%r)" % self.name

        def format_full(self):
            return "\t".join([str(x) for x in [self] + list(self.addresses)])

    # Caching options.   A set of three RelationshipCache options
    # which can be applied to Query(), causing the "lazy load"
    # of these attributes to be loaded from cache.
    cache_address_bits = (
        RelationshipCache(PostalCode.city, "default")
        .and_(RelationshipCache(City.country, "default"))
        .and_(RelationshipCache(Address.postal_code, "default"))
    )

    bootstrap()