SQLAlchemy eager loading multiple relationships

Question

SQLAlchemy supports eager load for relationship, it is basically a JOIN statement. However, if a model has two or more relationships, it could be a very huge join.

Answer 1

For a one-to-many or many-to-many relationship, it's (usually) better to use subqueryload instead, for performance reasons:

session.query(Product).join(User.addresses)\
    .options(subqueryload(Product.orders),\
             subqueryload(Product.tags)).all()

This issues separate SELECT queries for each of orders and tags.