CODEWITHSUNDEEP
pythonflasksqlalchemyflask-sqlalchemy
user14791349
user14791349

Reputation:

How do you update table to accommodate new column?

I edited my table by adding the column "post_id" to define the relationship between posts and replies (I'm trying to add comments to my flask application). So now when ever I run my site I get the error:

sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) table reply has no column named post_id [SQL: 'INSERT INTO reply (title, date_posted, content, user_id, post_id) VALUES (?, ?, ?, ?, ?)'] [parameters: ('testtitle', '2020-12-15 04:52:48.159734', 'testcontent', 5, None)]

so I try to update it by inserting the line:

reply.__table__.update(reply)

but then I get the error

sqlalchemy.exc.ArgumentError: SQL expression object or string expected, got object of type <class 'flask_sqlalchemy.model.DefaultMeta'> instead

My code for reference (please tell me if there is anything wrong with it I am very new to flask and SQLalchemy):

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100), nullable=False)
    date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    content = db.Column(db.Text, nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
    replys = db.relationship('Reply', backref='post', lazy=True)

    def get_replys(self):
        return Reply.query.filter_by(post_id=Post.id).order_by(Reply.timestamp.desc())


    def __repr__(self):
        return f"Post('{self.title}', '{self.date_posted}')"


class Reply(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100), nullable=False)
    date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    content = db.Column(db.Text, nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
    post_id = db.Column(db.Integer, db.ForeignKey('post.id'), nullable=False)




    def __repr__(self):
        return f"Reply('{self.title}', '{self.date_posted}')"

routes.py

@app.route("/post/reply", methods=['GET', 'POST'])
@login_required
def new_reply():
    form = ReplyForm()
    if form.validate_on_submit():
        reply = Reply(title=form.title.data, content=form.content.data, author=current_user,)
        db.session.add(reply)
        db.session.commit()
        flash('reply posted', 'success')
        return redirect(url_for('home'))
    return render_template('Reply.html', title='New Reply', form=form, legend='New Reply',)

Upvotes: 2

Views: 98

Answers (1)

Abdur-Rahmaan Janhangeer
Abdur-Rahmaan Janhangeer

Reputation: 621

After adding a new column, you need to add migrations. Migration is the process of applying your code changes to the database. In Flask a nice package if flask-migrate which is Alembic wrapped for Flask. You configure it like:

migrate.init_app(app, db)

The commands are, after configuring flask:

$ flask db init # first time
$ flask db migrate
$ flask db upgrade

Try the package!

Upvotes: 1

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