Suppose I have the standard M:N association table pattern, like so
class Xs(ModelBase):
id = Column(Integer, primary_key=True)
ys = relationship('Ys', secondary='test.xy_assoc', back_populates='xs')
class Ys(ModelBase):
id = Column(Integer, primary_key=True)
xs = relationship('Xs', secondary='test.xy_assoc', back_populates='ys')
class XY_assoc(ModelBase):
x_id = Column(Integer, ForeignKey(Xs.id), primary_key=True)
y_id = Column(Integer, ForeignKey(Ys.id), primary_key=True)
Everything is fine and works. But now I want to add a few extra
relationships to the association table itself:
class Xs(ModelBase):
id = Column(Integer, primary_key=True)
ys = relationship('Ys', secondary='test.xy_assoc', back_populates='xs')
xy_assocs = relationship('XY_assoc', back_populates='x')
class Ys(ModelBase):
id = Column(Integer, primary_key=True)
xs = relationship('Xs', secondary='test.xy_assoc', back_populates='ys')
xy_assocs = relationship('XY_assoc', back_populates='y')
class XY_assoc(ModelBase):
x_id = Column(Integer, ForeignKey(Xs.id), primary_key=True)
y_id = Column(Integer, ForeignKey(Ys.id), primary_key=True)
x = relationship('Xs', back_populates='xy_assocs')
y = relationship('Ys', back_populates='xy_assocs')
With this, I get the following SQLA warnings. What is the right way to
achieve this?
/var/folders/lk/x4t5tp_n28qgpyp14fr6r5700000gn/T/ipykernel_74888/982636505.py:2:
SAWarning: relationship 'Xs.xy_assocs' will copy column xs.id to column
xy_assoc.x_id, which conflicts with relationship(s): 'Xs.ys' (copies xs.id
to xy_assoc.x_id). If this is not the intention, consider if these
relationships should be linked with back_populates, or if viewonly=True
should be applied to one or more if they are read-only. For the less common
case that foreign key constraints are partially overlapping, the
orm.foreign() annotation can be used to isolate the columns that should be
written towards. To silence this warning, add the parameter 'overlaps="ys"'
to the 'Xs.xy_assocs' relationship. xs = session.query(Xs).all()
/var/folders/lk/x4t5tp_n28qgpyp14fr6r5700000gn/T/ipykernel_74888/982636505.py:2:
SAWarning: relationship 'Ys.xs' will copy column xs.id to column
xy_assoc.x_id, which conflicts with relationship(s): 'Xs.xy_assocs' (copies
xs.id to xy_assoc.x_id). If this is not the intention, consider if these
relationships should be linked with back_populates, or if viewonly=True
should be applied to one or more if they are read-only. For the less common
case that foreign key constraints are partially overlapping, the
orm.foreign() annotation can be used to isolate the columns that should be
written towards. To silence this warning, add the parameter
'overlaps="xy_assocs"' to the 'Ys.xs' relationship. xs =
session.query(Xs).all()
/var/folders/lk/x4t5tp_n28qgpyp14fr6r5700000gn/T/ipykernel_74888/982636505.py:2:
SAWarning: relationship 'Ys.xy_assocs' will copy column ys.id to column
xy_assoc.y_id, which conflicts with relationship(s): 'Xs.ys' (copies ys.id
to xy_assoc.y_id), 'Ys.xs' (copies ys.id to xy_assoc.y_id). If this is not
the intention, consider if these relationships should be linked with
back_populates, or if viewonly=True should be applied to one or more if
they are read-only. For the less common case that foreign key constraints
are partially overlapping, the orm.foreign() annotation can be used to
isolate the columns that should be written towards. To silence this
warning, add the parameter 'overlaps="xs,ys"' to the 'Ys.xy_assocs'
relationship. xs = session.query(Xs).all()
/var/folders/lk/x4t5tp_n28qgpyp14fr6r5700000gn/T/ipykernel_74888/982636505.py:2:
SAWarning: relationship 'XY_assoc.x' will copy column xs.id to column
xy_assoc.x_id, which conflicts with relationship(s): 'Xs.ys' (copies xs.id
to xy_assoc.x_id), 'Ys.xs' (copies xs.id to xy_assoc.x_id). If this is not
the intention, consider if these relationships should be linked with
back_populates, or if viewonly=True should be applied to one or more if
they are read-only. For the less common case that foreign key constraints
are partially overlapping, the orm.foreign() annotation can be used to
isolate the columns that should be written towards. To silence this
warning, add the parameter 'overlaps="xs,ys"' to the 'XY_assoc.x'
relationship. xs = session.query(Xs).all()
/var/folders/lk/x4t5tp_n28qgpyp14fr6r5700000gn/T/ipykernel_74888/982636505.py:2:
SAWarning: relationship 'XY_assoc.y' will copy column ys.id to column
xy_assoc.y_id, which conflicts with relationship(s): 'Xs.ys' (copies ys.id
to xy_assoc.y_id), 'Ys.xs' (copies ys.id to xy_assoc.y_id). If this is not
the intention, consider if these relationships should be linked with
back_populates, or if viewonly=True should be applied to one or more if
they are read-only. For the less common case that foreign key constraints
are partially overlapping, the orm.foreign() annotation can be used to
isolate the columns that should be written towards. To silence this
warning, add the parameter 'overlaps="xs,ys"' to the 'XY_assoc.y'
relationship. xs = session.query(Xs).all()
--
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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