SQLAlchemy not committing changes to postgres

Question

I am having trouble committing database changes using SQLAlchemy and I cannot figure out why.

Here is the data model in question:

class EmailGroup(db.Model):
    __tablename__ = 'email_group'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(), unique=True, nullable=False)
    data = db.Column(db.JSON)

def __init__(self, name):
    self.name = name
    self.data = {u'members': []}

def addUser(self, username):
    data = self.data
    if username not in data[u'members']:
        data[u'members'].append(username)
        self.data = data

Here is the server code:

@app.route('/emailgroup/<groupid>/adduser/<userid>', methods=['POST'])
@jwt_required()
def emailGroupAddUser(groupid, userid):
    emailgroup = EmailGroup.query.filter_by(id=groupid).first()
    if not emailgroup:
        return 'Group with id ' + groupid + ' does not exist.', status.HTTP_400_BAD_REQUEST
    user = User.query.filter_by(id=userid).first()
    if not user:
        return 'User with id ' + userid + ' does not exist.', status.HTTP_400_BAD_REQUEST
    emailgroup.addUser(user.username)
    print emailgroup.dumps() # Is correctly updated here
    db.session.add(emailgroup)
    db.session.commit()
    print emailgroup.dumps() # Changes did not go through!
    return jsonify(emailgroup.dumps())

I have also tried using db.session.flush() instead of add/commit , which makes the two print statements print the correct outputs, but does not actually update the database still.

EDIT: I also tried using the Array type in SQLAlchemy but faced the same exact issue.

Answer 1

When dealing with JSON columns, you can call flag_modified rather than try to use the mutable extensions on arbitrary levels of nesting:

from sqlalchemy.orm.attributes import flag_modified

def addUser(self, username):
    data = self.data
    if username not in data[u'members']:
        data[u'members'].append(username)
        flag_modified(self, 'data')