examples.performance.short_selects — SQLAlchemy 2.0 Documentation

Release: 2.0.48 | Release Date: March 2, 2026

# SQLAlchemy 2.0 Documentation

# Source code for examples.performance.short_selects

    """This series of tests illustrates different ways to SELECT a single
    record by primary key

    """

    import random

    from sqlalchemy import bindparam
    from sqlalchemy import Column
    from sqlalchemy import create_engine
    from sqlalchemy import Identity
    from sqlalchemy import Integer
    from sqlalchemy import select
    from sqlalchemy import String
    from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy.future import select as future_select
    from sqlalchemy.orm import deferred
    from sqlalchemy.orm import Session
    from . import Profiler

    Base = declarative_base()
    engine = None

    ids = range(1, 11000)

    class Customer(Base):
        __tablename__ = "customer"
        id = Column(Integer, Identity(), primary_key=True)
        name = Column(String(255))
        description = Column(String(255))
        q = Column(Integer)
        p = Column(Integer)
        x = deferred(Column(Integer))
        y = deferred(Column(Integer))
        z = deferred(Column(Integer))

    Profiler.init("short_selects", num=10000)

    @Profiler.setup
    def setup_database(dburl, echo, num):
        global engine
        engine = create_engine(dburl, echo=echo, query_cache_size=0)
        Base.metadata.drop_all(engine)
        Base.metadata.create_all(engine)
        sess = Session(engine)
        sess.add_all(
            [
                Customer(
                    id=i,
                    name="c%d" % i,
                    description="c%d" % i,
                    q=i * 10,
                    p=i * 20,
                    x=i * 30,
                    y=i * 40,
                )
                for i in ids
            ]
        )
        sess.commit()

    @Profiler.profile
    def test_orm_query_classic_style(n):
        """classic ORM query of the full entity, no cache"""
        session = Session(bind=engine)
        for id_ in random.sample(ids, n):
            session.query(Customer).filter(Customer.id == id_).one()

    @Profiler.profile
    def test_orm_query_classic_style_w_cache(n):
        """classic ORM query of the full entity, using cache"""
        cache = {}
        session = Session(bind=engine.execution_options(compiled_cache=cache))
        for id_ in random.sample(ids, n):
            session.query(Customer).filter(Customer.id == id_).one()

    @Profiler.profile
    def test_orm_query_new_style(n):
        """new style ORM select() of the full entity, no cache."""

        session = Session(bind=engine)
        for id_ in random.sample(ids, n):
            stmt = future_select(Customer).where(Customer.id == id_)
            session.execute(stmt).scalar_one()

    @Profiler.profile
    def test_orm_query_new_style_cache(n):
        """new style ORM select() of the full entity, using cache."""

        cache = {}
        session = Session(bind=engine.execution_options(compiled_cache=cache))
        for id_ in random.sample(ids, n):
            stmt = future_select(Customer).where(Customer.id == id_)
            session.execute(stmt).scalar_one()

    @Profiler.profile
    def test_orm_query_classic_style_cols_only(n):
        """classic ORM query against columns, no cache"""
        session = Session(bind=engine)
        for id_ in random.sample(ids, n):
            session.query(Customer.id, Customer.name, Customer.description).filter(
                Customer.id == id_
            ).one()

    @Profiler.profile
    def test_orm_query_classic_style_cols_only_cache(n):
        """classic ORM query against columns, using cache"""
        cache = {}
        session = Session(bind=engine.execution_options(compiled_cache=cache))
        for id_ in random.sample(ids, n):
            session.query(Customer.id, Customer.name, Customer.description).filter(
                Customer.id == id_
            ).one()

    @Profiler.profile
    def test_core_new_stmt_each_time(n):
        """test core, creating a new statement each time, no cache"""

        with engine.connect() as conn:
            for id_ in random.sample(ids, n):
                stmt = select(Customer.__table__).where(Customer.id == id_)
                row = conn.execute(stmt).first()
                tuple(row)

    @Profiler.profile
    def test_core_new_stmt_each_time_compiled_cache(n):
        """test core, creating a new statement each time, using cache"""

        compiled_cache = {}
        with engine.connect().execution_options(
            compiled_cache=compiled_cache
        ) as conn:
            for id_ in random.sample(ids, n):
                stmt = select(Customer.__table__).where(Customer.id == id_)
                row = conn.execute(stmt).first()
                tuple(row)

    @Profiler.profile
    def test_core_reuse_stmt(n):
        """test core, reusing the same statement, no cache"""

        stmt = select(Customer.__table__).where(Customer.id == bindparam("id"))
        with engine.connect() as conn:
            for id_ in random.sample(ids, n):
                row = conn.execute(stmt, {"id": id_}).first()
                tuple(row)

    @Profiler.profile
    def test_core_reuse_stmt_compiled_cache(n):
        """test core, reusing the same statement, using cache"""

        stmt = select(Customer.__table__).where(Customer.id == bindparam("id"))
        compiled_cache = {}
        with engine.connect().execution_options(
            compiled_cache=compiled_cache
        ) as conn:
            for id_ in random.sample(ids, n):
                row = conn.execute(stmt, {"id": id_}).first()
                tuple(row)

    if __name__ == "__main__":
        Profiler.main()