On 02/10/2016 01:01 PM, Dermot O'Sullivan wrote:
Hi guys,
Been trying to work this out. I have an existing database that I would
like to use sqlalchemy on. The code below is working in the sense that I
can query individual tables and joins do not fail ( where a FK reference
exists in the db ) but I can't seem to get references working.
engine = create_engine("postgresql:///local")
metadata = MetaData()
metadata.reflect(engine, only=['a', 'b'])
Base = automap_base(metadata=metadata)
class A(Base):
__tablename__ = 'table_a'
class B(Base):
__tablename__ = 'table_b'
a_ref = relationship('A', backref='b_ref')
Base.prepare(engine)
Note the 'only' in the metadata is because there are some tables in the
database causing trouble with the full reflect and I don't need them for
now so ignoring them. No errors when I load just these 2.
There is a real FK relationship in the database from B to A ( and I can
see it gets reflected properly in b.__table__.foreign_keys ) but for
some reason 'a_ref' is not defined on the instance returned by queries (
so instance.a_ref would throw an AttributeError ). I know it must be
something small I'm missing but I can't seem to get it.
if you are querying as session.query(B), there has to be an a_ref on the
B objects you get back. How are you querying? Can you provide a full
example of table defs and use ?
Any help would be appreciated.
Cheers,
Dermot
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