How can I perform efficient bulk inserts with SQLAlchemy ORM?

Bulk Inserts Using SQLAlchemy ORM

When inserting data into a database, efficiency is crucial. By default, SQLAlchemy inserts individual objects into tables, which can take longer for bulk operations.

Does SQLAlchemy Support Bulk Inserts?

Yes. Starting with version 1.0.0, SQLAlchemy includes bulk operations. These allow you to perform bulk inserts or updates in a single transaction.

How to Perform Bulk Inserts

To perform a bulk insert using SQLAlchemy ORM, follow these steps:

1. Create a list of objects that you want to insert.
2. Call the bulk_save_objects() method of your session passing the list of objects as an argument.
3. Commit the session to complete the insert operation.

For example:

s = Session()
objects = [
    User(name="u1"),
    User(name="u2"),
    User(name="u3")
]
s.bulk_save_objects(objects)
s.commit()

Enhancing Performance with Sessions

By default, SQLAlchemy commits every operation immediately. To improve performance for bulk inserts, you can disable auto-commit and manually commit after all objects are added. This ensures that data is loaded into the database in a single transaction. However, note that disabling auto-commit may lead to data consistency issues if errors occur.

To disable auto-commit, set the autocommit parameter to False when creating the session. Then, manually commit the session after all objects are added:

s = Session(autocommit=False)
s.bulk_save_objects(objects)
s.commit()

By using bulk operations and optimizing session usage, you can significantly improve the performance of your SQLAlchemy ORM applications for bulk data insertion tasks.

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