Currently, this is something that is not well supported, but not impossible to do. See this issue on the Flask-SQLAlchemy issue list, which admits that the current implementation of the extension makes this situation more of a headache than they think it should. Hopefully this will be better supported in the future (once a solid migration path and new API is determined).
That issue gives the following code sample:
from flask import Flask
from models import Base, User # Your non-Flask-SQLAlchemy models...
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
db = SQLAlchemy(app)
@app.before_first_request
def setup():
# Recreate database each time for demo
Base.metadata.drop_all(bind=db.engine)
Base.metadata.create_all(bind=db.engine)
db.session.add(User('Bob Jones', '[email protected]'))
db.session.add(User('Joe Quimby', '[email protected]'))
db.session.commit()
@app.route('/')
def root():
users = db.session.query(User).all()
return u"<br>".join([u"{0}: {1}".format(user.name, user.email) for user in users])
if __name__ == '__main__':
app.run('127.0.0.1', 5000)
There are a few things to note here:
First, you lose the ability to do User.query
(because User was created using its own declarative base), along with all of the other stuff that Flask-SQLAlchemy's db.Model gives you (such as the ability to auto-generate the table names and methods like first_or_404()
).
Second, any time you need to do things that involve the metadata (such as drop_all or create_all), you cannot use the Flask-SQLAlchemy methods. You must use the original metadata, bound to the Flask-SQLAlchemy engine.
I haven't tried this myself, so I'm not sure if there are any other gotchas to this approach. You might want to participate in that ticket if you find any.
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