eager_relations.py

SQLAlchemy. 经典的Python ORM框架。学习必看。

        mapper(User, users, properties={
            'addresses':relation(Address, lazy=False),
            'orders':relation(Order, lazy=False)
        })
        mapper(Address, addresses)
        mapper(Order, orders)

        allusers = create_session().query(User).all()

        # using a textual select, the columns will be 'id' and 'name'.
        # the eager loaders have aliases which should not hit on those columns, they should
        # be required to locate only their aliased/fully table qualified column name.
        noeagers = create_session().query(User).from_statement("select * from users").all()
        assert 'orders' not in noeagers[0].__dict__
        assert 'addresses' not in noeagers[0].__dict__

    @testing.fails_on('maxdb')
    def test_limit(self):
        """test limit operations combined with lazy-load relationships."""

        mapper(Item, items)
        mapper(Order, orders, properties={
            'items':relation(Item, secondary=order_items, lazy=False, order_by=items.c.id)
        })
        mapper(User, users, properties={
            'addresses':relation(mapper(Address, addresses), lazy=False, order_by=addresses.c.id),
            'orders':relation(Order, lazy=True)
        })

        sess = create_session()
        q = sess.query(User)

        if testing.against('mysql'):
            l = q.limit(2).all()
            assert fixtures.user_all_result[:2] == l
        else:
            l = q.limit(2).offset(1).order_by(User.id).all()
            print fixtures.user_all_result[1:3]
            print l
            assert fixtures.user_all_result[1:3] == l

    def test_distinct(self):
        # this is an involved 3x union of the users table to get a lot of rows.
        # then see if the "distinct" works its way out.  you actually get the same
        # result with or without the distinct, just via less or more rows.
        u2 = users.alias('u2')
        s = union_all(u2.select(use_labels=True), u2.select(use_labels=True), u2.select(use_labels=True)).alias('u')

        mapper(User, users, properties={
            'addresses':relation(mapper(Address, addresses), lazy=False),
        })

        sess = create_session()
        q = sess.query(User)

        def go():
            l = q.filter(s.c.u2_id==User.c.id).distinct().all()
            assert fixtures.user_address_result == l
        self.assert_sql_count(testing.db, go, 1)

    @testing.fails_on('maxdb')
    def test_limit_2(self):
        mapper(Keyword, keywords)
        mapper(Item, items, properties = dict(
                keywords = relation(Keyword, secondary=item_keywords, lazy=False, order_by=[keywords.c.id]),
            ))

        sess = create_session()
        q = sess.query(Item)
        l = q.filter((Item.c.description=='item 2') | (Item.c.description=='item 5') | (Item.c.description=='item 3')).\
            order_by(Item.id).limit(2).all()

        assert fixtures.item_keyword_result[1:3] == l

    @testing.fails_on('maxdb')
    def test_limit_3(self):
        """test that the ORDER BY is propigated from the inner select to the outer select, when using the
        'wrapped' select statement resulting from the combination of eager loading and limit/offset clauses."""

        mapper(Item, items)
        mapper(Order, orders, properties = dict(
                items = relation(Item, secondary=order_items, lazy=False)
        ))

        mapper(Address, addresses)
        mapper(User, users, properties = dict(
            addresses = relation(Address, lazy=False),
            orders = relation(Order, lazy=False),
        ))
        sess = create_session()

        q = sess.query(User)

        if not testing.against('maxdb', 'mssql'):
            l = q.join('orders').order_by(Order.user_id.desc()).limit(2).offset(1)
            assert [
                User(id=9,
                    orders=[Order(id=2), Order(id=4)],
                    addresses=[Address(id=5)]
                ),
                User(id=7,
                    orders=[Order(id=1), Order(id=3), Order(id=5)],
                    addresses=[Address(id=1)]
                )
            ] == l.all()

        l = q.join('addresses').order_by(Address.email_address.desc()).limit(1).offset(0)
        assert [
            User(id=7,
                orders=[Order(id=1), Order(id=3), Order(id=5)],
                addresses=[Address(id=1)]
            )
        ] == l.all()

    def test_limit_4(self):
        # tests the LIMIT/OFFSET aliasing on a mapper against a select.   original issue from ticket #904
        sel = select([users, addresses.c.email_address], users.c.id==addresses.c.user_id).alias('useralias')
        mapper(User, sel, properties={
            'orders':relation(Order, primaryjoin=sel.c.id==orders.c.user_id, lazy=False)
        })
        mapper(Order, orders)

        sess = create_session()
        self.assertEquals(sess.query(User).first(),
            User(name=u'jack',orders=[
                Order(address_id=1,description=u'order 1',isopen=0,user_id=7,id=1),
                Order(address_id=1,description=u'order 3',isopen=1,user_id=7,id=3),
                Order(address_id=None,description=u'order 5',isopen=0,user_id=7,id=5)],
            email_address=u'[e-mail]',id=7)
        )

    def test_one_to_many_scalar(self):
        mapper(User, users, properties = dict(
            address = relation(mapper(Address, addresses), lazy=False, uselist=False)
        ))
        q = create_session().query(User)

        def go():
            l = q.filter(users.c.id == 7).all()
            assert [User(id=7, address=Address(id=1))] == l
        self.assert_sql_count(testing.db, go, 1)

    @testing.fails_on('maxdb')
    def test_many_to_one(self):
        mapper(Address, addresses, properties = dict(
            user = relation(mapper(User, users), lazy=False)
        ))
        sess = create_session()
        q = sess.query(Address)

        def go():
            a = q.filter(addresses.c.id==1).one()
            assert a.user is not None
            u1 = sess.query(User).get(7)
            assert a.user is u1
        self.assert_sql_count(testing.db, go, 1)


    def test_one_and_many(self):
        """tests eager load for a parent object with a child object that
        contains a many-to-many relationship to a third object."""

        mapper(User, users, properties={
            'orders':relation(Order, lazy=False)
        })
        mapper(Item, items)
        mapper(Order, orders, properties = dict(
                items = relation(Item, secondary=order_items, lazy=False, order_by=items.c.id)
            ))

        q = create_session().query(User)

        l = q.filter("users.id in (7, 8, 9)")

        def go():
            assert fixtures.user_order_result[0:3] == l.all()
        self.assert_sql_count(testing.db, go, 1)

    def test_double_with_aggregate(self):

        max_orders_by_user = select([func.max(orders.c.id).label('order_id')], group_by=[orders.c.user_id]).alias('max_orders_by_user')

        max_orders = orders.select(orders.c.id==max_orders_by_user.c.order_id).alias('max_orders')

        mapper(Order, orders)
        mapper(User, users, properties={
               'orders':relation(Order, backref='user', lazy=False),
               'max_order':relation(mapper(Order, max_orders, non_primary=True), lazy=False, uselist=False)
               })
        q = create_session().query(User)

        def go():
            assert [
                User(id=7, orders=[
                        Order(id=1),
                        Order(id=3),
                        Order(id=5),
                    ],
                    max_order=Order(id=5)
                ),
                User(id=8, orders=[]),
                User(id=9, orders=[Order(id=2),Order(id=4)],
                    max_order=Order(id=4)
                ),
                User(id=10),
            ] == q.all()
        self.assert_sql_count(testing.db, go, 1)

    def test_wide(self):
        mapper(Order, orders, properties={'items':relation(Item, secondary=order_items, lazy=False, order_by=items.c.id)})
        mapper(Item, items)
        mapper(User, users, properties = dict(
            addresses = relation(mapper(Address, addresses), lazy = False),
            orders = relation(Order, lazy = False),
        ))
        q = create_session().query(User)
        l = q.all()
        assert fixtures.user_all_result == q.all()

    def test_against_select(self):
        """test eager loading of a mapper which is against a select"""

        s = select([orders], orders.c.isopen==1).alias('openorders')

        mapper(Order, s, properties={
            'user':relation(User, lazy=False)
        })
        mapper(User, users)
        mapper(Item, items)

        q = create_session().query(Order)
        assert [
            Order(id=3, user=User(id=7)),
            Order(id=4, user=User(id=9))
        ] == q.all()

        q = q.select_from(s.join(order_items).join(items)).filter(~Item.id.in_([1, 2, 5]))
        assert [
            Order(id=3, user=User(id=7)),
        ] == q.all()

    def test_aliasing(self):
        """test that eager loading uses aliases to insulate the eager load from regular criterion against those tables."""

        mapper(User, users, properties = dict(
            addresses = relation(mapper(Address, addresses), lazy=False)
        ))
        q = create_session().query(User)
        l = q.filter(addresses.c.email_address == '[e-mail]').filter(Address.user_id==User.id)
        assert fixtures.user_address_result[1:2] == l.all()

class AddEntityTest(FixtureTest):
    keep_mappers = False
    keep_data = True

    def _assert_result(self):
        return [
            (
                User(id=7,
                    addresses=[Address(id=1)]
                ),
                Order(id=1,
                    items=[Item(id=1), Item(id=2), Item(id=3)]
                ),
            ),
            (
                User(id=7,
                    addresses=[Address(id=1)]
                ),
                Order(id=3,
                    items=[Item(id=3), Item(id=4), Item(id=5)]
                ),
            ),
            (
                User(id=7,
                    addresses=[Address(id=1)]
                ),
                Order(id=5,
                    items=[Item(id=5)]
                ),
            ),
            (
                 User(id=9,
                    addresses=[Address(id=5)]
                ),
                 Order(id=2,
                    items=[Item(id=1), Item(id=2), Item(id=3)]
                ),
             ),
             (
                  User(id=9,
                    addresses=[Address(id=5)]
                ),
                  Order(id=4,
                    items=[Item(id=1), Item(id=5)]
                ),
              )
        ]

    def test_basic(self):
        mapper(User, users, properties={
            'addresses':relation(Address, lazy=False),
            'orders':relation(Order)
        })
        mapper(Address, addresses)
        mapper(Order, orders, properties={
            'items':relation(Item, secondary=order_items, lazy=False, order_by=items.c.id)
        })