Database session management in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of database session management in FastAPI?

It manages the connection to the database for each request, ensuring data consistency and proper resource use by opening and closing sessions as needed.

intermediate

How do you typically create a database session in FastAPI using SQLAlchemy?

You create a session factory with sessionmaker, then use a dependency function that yields a session and closes it after the request.

beginner

Why is it important to close the database session after each request?

Closing the session frees up database connections and avoids memory leaks, keeping the app efficient and stable.

intermediate

What does the 'yield' keyword do in the FastAPI dependency that manages the database session?

It provides the session to the path operation and then resumes to close the session after the request finishes.

advanced

How can you handle exceptions during database operations in a FastAPI session?

Use try-except blocks inside the session dependency or route, and rollback the session if an error occurs before closing it.

What is the main role of the sessionmaker in FastAPI database management?

A To handle HTTP requests

B To close database connections automatically

C To define database models

D To create new database sessions

Sessionmaker creates new database session objects used to interact with the database.

In FastAPI, how do you ensure a database session is closed after a request?

A By manually calling close() in every route

B By using a dependency with yield and closing the session after yield

C By setting a global session variable

D By restarting the server

Using a dependency with yield allows automatic closing of the session after the request finishes.

What happens if you don't close database sessions properly in FastAPI?

A Database connections may leak and cause errors

B The app runs faster

C Nothing, sessions close automatically

D The database schema changes

Not closing sessions can cause connection leaks and degrade app performance.

Which Python keyword is used in FastAPI dependencies to manage setup and cleanup of database sessions?

A yield

B async

C return

D await

The yield keyword allows the function to provide a session and then continue to cleanup after.

How do you handle errors during database operations in a FastAPI session?

A Ignore errors and continue

B Close the session without rollback

C Use try-except and rollback the session on error

D Restart the database server

Using try-except and rolling back ensures the database stays consistent after errors.

Explain how to create and manage a database session in FastAPI using SQLAlchemy.

Think about how FastAPI dependencies help manage resources per request.

Describe why proper database session management is important in web applications.

Consider what happens if sessions stay open or errors are not handled.