[Sqlalchemy-tickets] Issue #3056: Materialized path relationship: `lazy="subquery"` not working while `subqueryload()` works (zzzeek/sqlalchemy)

[Jack Z. <iss...@bi...>]

New issue 3056: Materialized path relationship: `lazy="subquery"` not working while `subqueryload()` works
https://bitbucket.org/zzzeek/sqlalchemy/issue/3056/materialized-path-relationship-lazy

Jack Zhou:

Reference: http://stackoverflow.com/questions/23054398/materialized-path-relationship-in-declarative-sqlalchemy/23176477#comment36511621_23176477

The configuration:

```
#!python

class Node(Base):
    __tablename__ = "node"
    id = Column(Integer, primary_key=True)
    path = Column(String(500), nullable=False)
    children = relationship(
        "Node", primaryjoin=remote(foreign(path)).like(path.concat(".%")),
        viewonly=True, lazy="subquery")
```

The query:

```
#!python

db.add(Node(path="foo"))
db.add(Node(path="foo.bar"))
db.add(Node(path="foo.bar.baz"))
db.flush()

db.query(Node).all()  # issues one SELECT to find all nodes
db.query(Node).options(subqueryload(Node.children)).all()  # issues two SELECTs to find all nodes and their children
```

The `lazy="subquery"` declaration does not seem to have any effect.