SQL Alchemy - How to delete a model instance?

Question

Say I have a model instance like this:

instance = session.query(MyModel).filter_by(id=1).first()

How can I delete that row? Is there a special method to call?

Mcintire

Remember to use .get(1) instead of filter_by(id=1).first(), if 'id' is the primary key! This results in less database hits. Read: docs.sqlalchemy.org/en/latest/orm/… – Mesozoic

Answer 1

Ok I found it after further searching:

session.delete(instance)

Mcintire

I think this is better if you delete by id: MyModel.query.filter(MyModel.id == 123).delete() More direct. See #27159073 – Paralytic

I don't know about the original usecase behind this question but regardless, deleting with an id is not "better" or "more direct" in itself. It is just one of several options to get the job done. -- If I already have an instance, because I had to use it for other reasons, then it is clearly more direct to use session.delete(instance) rather than session.query(InstanceModel).filter_by(a=instance.a, ...).delete() (typical relation model). – Nauseate

Answer 2

You can fire a Single query for this.

For all records:

session.query(MyModel).delete()
session.commit()

It will delete all records from it and if you want to delete specific records then try filter clause in the query. ex.

For specific value:

session.query(MyModel).filter(MyModel.id==1).delete()
session.commit()

Lordling

I am getting sqlalchemy.exc.InvalidRequestError: SQL expression, column, or mapped entity expected - got '<class '__main__.ModelName'>'. – Annulet

Answer 3

For me, it's working with delete and commit:

session.delete(instance)
session.commit()

Mccready