Release: 2.0.48 | Release Date: March 2, 2026

# SQLAlchemy 2.0 Documentation

# Source code for examples.performance.bulk_updates

    """This series of tests will illustrate different ways to UPDATE a large number
    of rows in bulk (under construction! there's just one test at the moment)

    """

    from sqlalchemy import Column
    from sqlalchemy import create_engine
    from sqlalchemy import Identity
    from sqlalchemy import Integer
    from sqlalchemy import String
    from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy.orm import Session
    from . import Profiler

    Base = declarative_base()
    engine = None

    class Customer(Base):
        __tablename__ = "customer"
        id = Column(Integer, Identity(), primary_key=True)
        name = Column(String(255))
        description = Column(String(255))

    Profiler.init("bulk_updates", num=100000)

    @Profiler.setup
    def setup_database(dburl, echo, num):
        global engine
        engine = create_engine(dburl, echo=echo)
        Base.metadata.drop_all(engine)
        Base.metadata.create_all(engine)

        s = Session(engine)
        for chunk in range(0, num, 10000):
            s.bulk_insert_mappings(
                Customer,
                [
                    {
                        "name": "customer name %d" % i,
                        "description": "customer description %d" % i,
                    }
                    for i in range(chunk, chunk + 10000)
                ],
            )
        s.commit()

    @Profiler.profile
    def test_orm_flush(n):
        """UPDATE statements via the ORM flush process."""
        session = Session(bind=engine)
        for chunk in range(0, n, 1000):
            customers = (
                session.query(Customer)
                .filter(Customer.id.between(chunk, chunk + 1000))
                .all()
            )
            for customer in customers:
                customer.description += "updated"
            session.flush()
        session.commit()