On 12/08/2016 08:44 PM, b...@sfi.ca wrote:
Hi,
Running SQLAlchemy==1.1.4
I'm getting this
AmbiguousForeignKeysError: Could not determine join condition
between parent/child tables on relationship Artifact.slaves - there
are multiple foreign key paths linking the tables. Specify the
'foreign_keys' argument, providing a list of those columns which
should be counted as containing a foreign key reference to the
parent table.
and I'm wondering if I'll have to use primaryjoin= statement instead of
relying on foreign_keys= to work around this.
The code is shown below. I've included Artifact_Reference for
completeness but it's probably not needed.
when you build two relationship()s that are linked using back_populates,
the configuration for each relationship() has to be set up completely as
though that relationship were on its own. The one-to-many and
many-to-one relationships from a "foreign key" perspective are
essentially identical, they refer to the same structure in the database.
So in this specific example you need "foreign_keys" on both sides:
slaves = relationship("Artifact_Relation", back_populates="master",
foreign_keys="Artifact_Relation.slave_artifact_id")
masters = relationship("Artifact_Relation", back_populates="slave",
foreign_keys="Artifact_Relation.master_artifact_id")
if you were to instead build relationship on just one side, and the
other one were generated by "backref", then you wouldn't need this
double-configuration.
Is the problem on the Artifact_Relation model, or on the Artifact model?
I'm thinking the later, but I don't see any logical way to specify
foreign_keys on Artifact as it's on the one side of many to one.
I'm following this link for Artifact_Relation (i.e. Association
table)
http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#association-object
where Artifact serves as both the Parent and Child
I'm following this link for multiple-path
resolution
http://docs.sqlalchemy.org/en/latest/orm/join_conditions.html#relationship-foreign-keys
Even though Artifact is on both sides of the association, I can't see
needing to use backref() w/ remote_id to resolve this,
ala http://docs.sqlalchemy.org/en/latest/orm/self_referential.html
Thanks for any suggestions..
|
Base = declarative_base()
class Artifact_Relation(Base):
__tablename__ = 'artifact_relation'
master_artifact_id = Column(
Integer,
ForeignKey('artifact.id', name='artifact_relation_master_id_fk',
ondelete="cascade", onupdate="cascade"),
primary_key=True,
nullable=False
)
slave_artifact_id = Column(
Integer,
ForeignKey('artifact.id', name='artifact_relation_slave_id_fk',
ondelete="cascade", onupdate="cascade"),
primary_key=True,
nullable=False
)
relationship_type = Column(String(24), nullable=False)
slave = relationship("Artifact", back_populates="masters",
foreign_keys=[slave_artifact_id])
master = relationship("Artifact", back_populates="slaves",
foreign_keys=[master_artifact_id])
class Artifact(Base):
"Artifact"
__tablename__ = 'artifact'
id = Column('id', Integer, primary_key=True)
artifact_type = Column('artifact_type', String(16), nullable=False)
__mapper_args__ = {
'polymorphic_on': artifact_type
}
artifact_references = relationship(
'Artifact_Reference',
back_populates='artifact',
cascade="all, delete-orphan",
passive_deletes=True
)
slaves = relationship("Artifact_Relation", back_populates="master")
masters = relationship("Artifact_Relation", back_populates="slave")
class Artifact_Reference(Base):
"""Artifact_Reference"""
__tablename__ = 'artifact_reference'
id = Column('id', Integer, primary_key=True)
type = Column('type', String(24), nullable=False)
artifact_id = Column('artifact_id', Integer, ForeignKey(Artifact.id,
name="artifact_reference_artifact_id_fk", ondelete="cascade",
onupdate="cascade"), nullable=False)
reference = Column('reference', String(64), nullable=False)
artifact = relationship(
Artifact,
back_populates='artifact_references'
)
Index('reference_idx', reference, unique=False)
|
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SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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