Let's say I have acquisitions at regular intervals and each
acquisition I get different measures.
Each meausre has a value and a numeric type id (1 = temperature, 2 =
humidity ecc...)
I want user to insert text description for type id he knows, if he
wants.
I end up having this 3 tables:
measures = Table('measure', metadata,
Column('id', Integer, primary_key=True),
Column('acq_id', Integer, ForeignKey('acquisitions.id'),
nullable=False)
Column('type_id', Integer, ForeignKey('types.id'),
nullable=False),
Column('value', Float, nullable=False),
)
acquisitions = Table('acquisitions', metadata,
Column('id', Integer, primary_key=True),
Column('datetime', DateTime, nullable=False),
)
types = Table('types', metadata,
Column('id', Integer, primary_key=True, autoincrement=False),
Column('desc', String, nullable=False),
)
[class definitions...]
orm.mapper(Acquisition, acquisitions)
orm.mapper(Type, types)
orm.mapper(Measures, measure, properties={
'type': orm.relationship(Type, backref='measures'),
'acquisition': orm.relationship(Acquisition, backref='measures'),
})
Now, while I want, deleting an acquisition, all child measures are
deleted too,
I DON'T want any modification in data if the user edit types, for
example:
- deletes a type (related measures are not deleted and their type_id
is not changed in null value)
- edits the type.id (precedent associated measures are not updated to
new type_id but mantain the old one).
How can I achieve this?
I guess I should use cascade in relationship but can't figure how
Thanks for your support!
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