I have this 4 tables, the base concept is:
`sensor data comes from its id_meas / id_cu pair, I can find id_meas
directly in data and id_cu in data parent acquisition.`
data = Table('data', metadata,
Column('id', Integer, primary_key=True),
Column('id_acq', Integer, ForeignKey('acquisitions.id'),
nullable=False),
Column('id_meas', Integer, nullable=False),
Column('value', Float, nullable=True),
)
acquisitions = Table('acquisitions', metadata,
Column('id', Integer, primary_key=True),
Column('id_cu', Integer, ForeignKey('ctrl_units.id'),
nullable=False),
Column('datetime', DateTime, nullable=False),
)
sensors = Table('sensors', metadata,
Column('id_cu', Integer, ForeignKey('ctrl_units.id'),
primary_key=True,
autoincrement=False),
Column('id_meas', Integer, primary_key=True, autoincrement=False),
Column('name', Unicode(20), nullable=False),
Column('desc', Unicode(40), nullable=False),
)
ctrl_units = Table('ctrl_units', metadata,
Column('id', Integer, primary_key=True, autoincrement=False),
Column('desc', Unicode(40), nullable=False)
)
and this mapping:
...
orm.mapper(Sensor, sensors,
properties={
'data': orm.relationship(Data, backref='sensor',
primaryjoin=and_(sensors.c.id_meas==data.c.id_meas,
data.c.id_acq==acquisitions.c.id,
acquisitions.c.id_cu==sensors.c.id_cu),
cascade='all, delete-orphan', single_parent=True)
})
...
and I can't get 'data' relationship to work, I get this error:
sqlalchemy.exc.ArgumentError: Could not locate any equated, locally
mapped column pairs for primaryjoin condition 'sensors.id_meas =
data.id_meas AND data.id_acq = acquisitions.id AND acquisitions.id_cu
= ctrl_units.id AND ctrl_units.id = sensors.id_cu' on relationship
Sensor.data. For more relaxed rules on join conditions, the
relationship may be marked as viewonly=True.
I also tried involving also ctr_units in primary join but had same
error.
Thanks for your support
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