Flask-SQLAlchemy's create_all does not create tables

Question

I'm working on a flask application where I'm trying to isolate my unit tests. I'm using flask-sqlalchemy, and I'm trying to use the create_all and drop_all methods to clean my database after running a test.

However, it appears my create_all and drop_all methods do not actually create/drop the tables as the documentation states. I have my models imported in the application before calling create_all, like most other answers say.

This is the error I'm getting with the code below:

psycopg2.ProgrammingError: relation "tasks" does not exist

Here's my relevant code

/app.py

import os
import configparser

from flask import Flask
from src.router import router

from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

app = Flask(__name__)

if not os.path.exists(os.path.join(app.root_path, 'config.ini')):
    raise Exception(f'config.ini not found in the {app.root_path}')

config = configparser.ConfigParser()
config.read('config.ini')

app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = config[os.environ['APP_ENV']]['DATABASE_URI']

app.register_blueprint(router)

db = SQLAlchemy(app)
migrate = Migrate(app, db)

if __name__ == "__main__":
    app.run()

/tests/test_router.py

from unittest import TestCase

from flask import Flask
from app import app, db
from src.models import Task

class TestRouter(TestCase):

    def setUp(self):
        db.create_all()

    def tearDown(self):
        db.drop_all()

    def test_adds_task(self):
        task = Task(task_id='task_1', name='my task')
        db.session.add(task)
        db.session.commit()

Brian Nystrom · Accepted Answer · 2018-04-13 16:26:03Z

1

I think I was a little quick to post the question, but I hope this might help others come up with other ideas on how to troubleshoot a similar issue.

In my src/models.py file where I keep my models, you must make sure that your models are defined correctly. Since Flask-SQLAlchemy is a wrapper around the SQLAlchemy you must use the data types under the db object.

Essentially, I had my models defined as such:

class Task(db.Model):
    __tablename__ = 'tasks'

    id = Column(Integer, primary_key=True)
    task_id = Column(String)
    name = Column(String)
    created_at = Column(DateTime, default=datetime.datetime.now)

As you can see, I was inheriting from db.Model instead of the return value of declarative_base(). I also needed to add the db. in front of all the data types, including Column, Integer, String, Float, DateTime, relationship, and ForeignKey.

So, I was able to fix my issue by changing my model to something like:

class Task(db.Model):
    __tablename__ = 'tasks'

    id = db.Column(db.Integer, primary_key=True)
    task_id = db.Column(db.String)
    name = db.Column(db.String)
    created_at = db.Column(db.DateTime, default=datetime.datetime.now)

See: Documentation on declaring Flask-SQLAlchemy models

answered Apr 13, 2018 at 16:26

Brian Nystrom

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1 Comment

Ilja Everilä Over a year ago

That's odd given that the names under db mostly reference the very same SQLAlchemy constructs: "flask_sqlalchemy.SQLAlchemy gives you access to the following things: all the functions and classes from sqlalchemy and sqlalchemy.orm ..."

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