How does one define a self-referential relationship when using
declarative objects and reflection? Based on
http://docs.sqlalchemy.org/en/rel_0_8/orm/relationships.html#adjacency-list-relationships
I wrote the code below but when I run it I get an exception when
the session.query() line is executed:
[...many frames elided...]
File "/usr/local/lib/python3.3/site-packages/sqlalchemy/sql/expression.py",
line 1551, in _only_column_elements
"'%s'; got: '%s', type %s" % (name, element, type(element)))
sqlalchemy.exc.ArgumentError: Column-based expression object expected for
argument 'remote_side'; got: '<built-in function id>', type <class
'builtin_function_or_method'>
Code:
----------------
import sqlalchemy as sa, sqlalchemy.orm, sqlalchemy.ext,
sqlalchemy.ext.declarative
Base = sa.ext.declarative.declarative_base
(cls=sa.ext.declarative.DeferredReflection)
class Test (Base):
__tablename__ = 'test'
parentobj = sa.orm.relationship ('Test', remote_side=[id])
connectstr = 'postgres://postgres@localhost/test6603976'
engine = sa.create_engine (connectstr)
connection = engine.connect()
meta = sa.MetaData()
meta.reflect (bind=engine)
Base.prepare (engine)
session = sa.orm.sessionmaker (bind=engine)()
session.query(Test).order_by(Test.id).all()
----------------
Database (postgresql):
CREATE TABLE test (
id INT PRIMARY KEY,
parent INT REFERENCES test(id));
INSERT INTO test VALUES (1, NULL),(2,1);
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