I'm new to Flask and web development in general. I have a Flask web-application that is using SQLAlchemy, is it ok to put session.rollback at the beginning of the app in order to keep it running even after a transaction fails?
I had a problem with my website when it stopped working after I was attempting to delete records of one table. The error log showed that the deletion failed due to entries in another table still referencing these records as their foreign key. The error log suggested using session.rollback to rollback this change, so I put it at the beginning of my app just after binding my database and creating the session and my website worked. This gave me the hint to leave that line there. Is my move right, safe and ok? Can anyone tell me what is the correct thing to do if this is somewhat endangering the functionality or logic of my website by any chance?
I'd say by that you are by definition cargo cult coding and should try to determine why you're finding these errors in the first place instead of just including a bit of code for a reason you don't understand.
The problem you're describing is the result of using foreign keys to ensure data integrity in your database. Typically SQLAlchemy will nullify all of the depending foreign keys, but since I don't know anything about your set up I can't explain why it wasn't. It is perhaps a difference between databases.
One massive problem with putting the rollback at the beginning of a route (or the entire global app) is that you might rollback data which you didn't want to. You haven't provided an MVCE so no one can really help you debug your problem.
Cargo cult coding in circumstances like this is understandable, but it's never a good practice. To solve this problem, investigate the cascades in SQLAlchemy. Also, fire up your actual SQL db interface and look at the data's structure, and set SQLALCHEMY_ECHO = 1 in your config file to see what's actually getting emitted.
Good luck!