Updates to JSON field don't persist to DB

Question

We have a model with a JSON field where user flags get inserted. Inserting does work as expected, but when removing certain flags, they stay in the field and changes don't get persisted to the DB.

We have the following method in our model:

def del_flag(self, key):     if self.user_flags is None or not key in self.user_flags:         return False     else:         del self.user_flags[key]         db.session.commit()                 return True 

The databasse is postgres and we use the SQLalchemy JSON field dialect for the field type. Any advice on this?

Answer 1

If you are using Postgres < 9.4 you can't update JSON field directly. You need flag_modified function to report the change to SQLAlchemy:

from sqlalchemy.orm.attributes import flag_modified model.data['key'] = 'New value' flag_modified(model, "data") session.add(model) session.commit() 

Answer 2

I'm using JSON field and I referred below document.

https://docs.sqlalchemy.org/en/13/core/type_basics.html?highlight=json#sqlalchemy.types.JSON

It shows how to make JSON-dict field mutable. (Default is immutable)

like this..

from sqlalchemy.ext.mutable import MutableDict from sqlalchemy import Column, Integer, JSON  class TableABC(Base):     __tablename__ = 'table_abc'     id = Column(Integer, primary_key=True)     info = Column(MutableDict.as_mutable(JSON))  

Then I could update json field as ORM.