Update not commited on mysql server flask-sqlalchemy

Question

I am able to perform 'select' queries to my Mysql database. However, the "insert" ones don't change the database, only the python objects. So when I restart the flask app, all the commited(?) editions are gone.

Views:

from flask import Flask, render_template, request, redirect, url_for, flash, Response
from sqlalchemy import exc
from models import *

app = Flask(__name__)
app.config['DEBUG'] = True
app.config['SECRET_KEY'] = 'kjhS7usfHGJHDez78'
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+mysqldb://admin:admin@127.0.0.1:3306/grenier'
app.config['SQLALCHEMY_ECHO'] = True
db = SQLAlchemy(app)

db.create_all()

@app.route('/ajax/submit_edition', methods=['POST'])
def submit_edition():
    if request.method == 'POST':
        given_id=1
        show = Shows.query.filter_by(id=given_id).first()
        show.short_description = "Hello"
        try:
            db.session.commit()
            db.session.flush()
            return "ok"
        except exc.SQLAlchemyError:
            return "Error in commiting the edition"

No particular exception is found. The route always returns "ok".

Models:

from sqlalchemy import Column, ForeignKey
from sqlalchemy.dialects.mysql import LONGTEXT, YEAR
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()


class Shows(db.Model):
    __tablename__ = "shows"

    id = Column(db.Integer, ForeignKey("programmation.id"), primary_key=True)
    date = Column(db.DATETIME)
    title = Column(db.VARCHAR(50))
    short_description = Column(db.VARCHAR(200))
    type = Column(db.VARCHAR(20))
    background_image = Column(db.VARCHAR(150))
    content = Column(LONGTEXT)

    def serialize(self, whatTo):
        result = {}
        if 'id' in whatTo:
            result['id'] = self.id
        if 'date' in whatTo:
            result['date'] = str(self.date)
        if 'title' in whatTo:
            result['title'] = self.title
        if 'short_description' in whatTo:
            result['short_description'] = self.short_description
        if 'type' in whatTo:
            result['type'] = self.type
        if 'background_image' in whatTo:
            result['background_image'] = self.background_image
        if 'content' in whatTo:
            result['content'] = self.content
        return result


class Programmation(db.Model):
    __tablename__ = "programmation"

    id = Column(db.Integer, primary_key=True)
    semester = Column(db.Integer)
    year = Column(YEAR)

When I look at the logs, the sql request is created for the select. But for the insert commit(), there is nothing.

Thank you !

Answer 1

The problem is usage of two different SQLAlchemy instance. When you call db.create_all() method it creates all tables which which inherited from db.Model but in your views you don't have any model inherited from db = SQLAlchemy(app) . All your models inherited from other SQLAlchemy instance. To fix this import the db object from views to models module and use it as parent class for inheritance:

#models.py
from views import db

#db = SQLAlchemy() #remove this line
class Show(db.Model):
    ...