selects.py

SQLAlchemy. 经典的Python ORM框架。学习必看。

import testenv; testenv.configure_for_tests()
from sqlalchemy import *
from sqlalchemy.orm import *
from testlib import *
from testlib.fixtures import Base


class InheritingSelectablesTest(ORMTest):
    def define_tables(self, metadata):
        global foo, bar, baz
        foo = Table('foo', metadata,
                    Column('a', String(30), primary_key=1),
                    Column('b', String(30), nullable=0))

        bar = foo.select(foo.c.b == 'bar').alias('bar')
        baz = foo.select(foo.c.b == 'baz').alias('baz')

    def test_load(self):
        # TODO: add persistence test also
        testing.db.execute(foo.insert(), a='not bar', b='baz')
        testing.db.execute(foo.insert(), a='also not bar', b='baz')
        testing.db.execute(foo.insert(), a='i am bar', b='bar')
        testing.db.execute(foo.insert(), a='also bar', b='bar')

        class Foo(Base): pass
        class Bar(Foo): pass
        class Baz(Foo): pass

        mapper(Foo, foo, polymorphic_on=foo.c.b)

        mapper(Baz, baz,
                    select_table=foo.join(baz, foo.c.b=='baz').alias('baz'),
                    inherits=Foo,
                    inherit_condition=(foo.c.a==baz.c.a),
                    inherit_foreign_keys=[baz.c.a],
                    polymorphic_identity='baz')

        mapper(Bar, bar,
                    select_table=foo.join(bar, foo.c.b=='bar').alias('bar'),
                    inherits=Foo,
                    inherit_condition=(foo.c.a==bar.c.a),
                    inherit_foreign_keys=[bar.c.a],
                    polymorphic_identity='bar')

        s = sessionmaker(bind=testing.db)()

        assert [Baz(), Baz(), Bar(), Bar()] == s.query(Foo).all()
        assert [Bar(), Bar()] == s.query(Bar).all()

if __name__ == '__main__':
    testenv.main()