Function async_main

examples/asyncio/gather_orm_statements.py:66–107

()

async def async_main():
    engine = create_async_engine(
        "postgresql+asyncpg://scott:tiger@localhost/test",
        echo=True,
    )

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.drop_all)
        await conn.run_sync(Base.metadata.create_all)

    async_session = async_sessionmaker(engine, expire_on_commit=False)

    async with async_session() as session, session.begin():
        session.add_all([A(data="a_%d" % i) for i in range(100)])

    statements = [
        select(A).where(A.data == "a_%d" % random.choice(range(100)))
        for i in range(30)
    ]

    frozen_results = await asyncio.gather(
        *(
            run_out_of_band(async_session, statement)
            for statement in statements
        )
    )
    results = [
        # merge_results means the ORM objects from the result
        # will be merged back into the original session.
        # load=False means we can use the objects directly without
        # re-selecting them.  however this merge operation is still
        # more expensive CPU-wise than a regular ORM load because the
        # objects are copied into new instances
        (
            await session.run_sync(
                merge_frozen_result, statement, result, load=False
            )
        )()
        for statement, result in zip(statements, frozen_results)
    ]

    print(f"results: {[r.all() for r in results]}")


asyncio.run(async_main())