Bulk inserts with Flask-SQLAlchemy

I use the following code to quickly read the content of a pandas DataFrame into SQLite. Note that it circumvents the ORM features of SQLAlchemy. myClass in this context is a db.Model derived class that has a tablename assigned to it. As the code snippets mentions, I adapted

l = df.to_dict('records')
# bulk save the dictionaries, circumventing the slow ORM interface
# c.f. https://gist.github.com/shrayasr/5df96d5bc287f3a2faa4
connection.engine.execute(
    myClass.__table__.insert(),
    l
)

Perhaps you should try to db.session.flush() to send the data to the server, which means any primary keys will be generated. At the end you can db.session.commit() to actually commit the transaction.