Hi Mike,
I am creating a graph structure using the ORM below and am able to do
inserts.
Base = declarative_base()
class Link(Base):
__tablename__ = 'base_link'
_constraints = ['first_id', 'second_id']
__table_args__ = (UniqueConstraint(*_constraints, name =
'link_constraint'), {"schema":"my_schema"})
id = Column(CHAR(32), primary_key=True)
object_type = Column(String(16))
first_id = Column(CHAR(32), ForeignKey(Node.id))
second_id = Column(CHAR(32), ForeignKey(Node.id))
orl1 =relationship('Node', foreign_keys=first_id)
orl2 =relationship('Node', foreign_keys=second_id)
class Node(Base):
__tablename__ = 'node'
_constraints = ['h_name', 'd_name']
__table_args__ = (UniqueConstraint(*_constraints, name='node_constraint'),
{"schema":"my_schema"})
h_name = Column(String(256),nullable=False)
d_name = Column(String(256),nullable=True)
id = Column(CHAR(32),primary_key=True)
I am having a hard time querying the above Objects
for example:
Case-1 (ref case-1.png):
my join was pretty much straightforward for Case-1.
Usage = aliased(Link, name = "Usage")
node_1 = aliased(Node, name = "node_1")
node_2 = aliased(Node, name = "node_2")
session.query(node_1, node_2).join(Usage, node_1.id ==
Usage.first_id).join(node_2, node_2.id == Usage.second_id)
How would my join be for my Case-2 (ref case-2.png)?
Usage = aliased(Link, name = "Usage")
Usage_2 = aliased(Link, name = "Usage_2")
node_1 = aliased(Node, name = "node_1")
node_2 = aliased(Node, name = "node_2")
node_3 = aliased(Node, name = "node_3")
I cannot quite properly build the query
the query below is as close as I can get
session.query(node_1, node_2, node_3).join(Usage,
node_1.id==Usage.first_id).join(Usage_2,
node_3.id==Usage_2.first_id).join(node_2,
and_(node_2.id==Usage.second_id, node_2.id==Usage_2.second_id))
which I know is wrong. It will be really nice if someone could point me in
the right direction for my case-2 join.
Regards,
Madhusudan Sridharan
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