CODEWITHSUNDEEP
pythonsqlalchemyflask-sqlalchemy
Kallie
Kallie

Reputation: 316

Default filter for Model in SQLAlchemy

Let's say I have the following table called my_table

id type
1 a
2 b
3 b
4 a

I want to have two models that rely on the same table, but when I query each they will return only results with a default filter on type column. So for example -

def filter_by_a():
    ...

def filter_by_b():
    ...

class ModelA(db.Model):
    __tablename__ = 'my_table'

    default_filter = filter_by_a

    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String)

class ModelB(db.Model):
    __tablename__ = 'my_table'

    default_filter = filter_by_b

    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String)

When I use db.session.query(ModelA) the results are

id type
1 a
4 a

And when I use db.session.query(ModelB) the results are

id type
2 b
3 b

Is there a way to do that?

Upvotes: 0

Views: 806

Answers (1)

Kallie
Kallie

Reputation: 316

https://docs.sqlalchemy.org/en/14/orm/inheritance.html#single-table-inheritance

class MyTableModel(db.Model):
    __tablename__ = 'my_table'
    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String)

    __mapper_args__ = {
        'polymorphic_on': type
    }

class ModelA(MyTableModel):
    __mapper_args__ = {
        'polymorphic_identity': 'a'
    }

class ModelB(MyTableModel):
    __mapper_args__ = {
        'polymorphic_identity': 'b'
    }

Upvotes: 1

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