Function main

examples/sharding/asyncio.py:268–346

()

async def main():
    await setup()

    # save and load objects!

    tokyo = WeatherLocation("Asia", "Tokyo")
    newyork = WeatherLocation("North America", "New York")
    toronto = WeatherLocation("North America", "Toronto")
    london = WeatherLocation("Europe", "London")
    dublin = WeatherLocation("Europe", "Dublin")
    brasilia = WeatherLocation("South America", "Brasila")
    quito = WeatherLocation("South America", "Quito")

    tokyo.reports.append(Report(80.0))
    newyork.reports.append(Report(75))
    quito.reports.append(Report(85))

    async with Session() as sess:
        sess.add_all(
            [tokyo, newyork, toronto, london, dublin, brasilia, quito]
        )

        await sess.commit()

        t = await sess.get(
            WeatherLocation,
            tokyo.id,
            options=[immediateload(WeatherLocation.reports)],
        )
        assert t.city == tokyo.city
        assert t.reports[0].temperature == 80.0

        # select across shards
        asia_and_europe = (
            await sess.execute(
                select(WeatherLocation).filter(
                    WeatherLocation.continent.in_(["Europe", "Asia"])
                )
            )
        ).scalars()

        assert {c.city for c in asia_and_europe} == {
            "Tokyo",
            "London",
            "Dublin",
        }

        # optionally set a shard id for the query and all related loaders
        north_american_cities_w_t = (
            await sess.execute(
                select(WeatherLocation)
                .filter(WeatherLocation.city.startswith("T"))
                .options(set_shard_id("north_america"))
            )
        ).scalars()

        # Tokyo not included since not in the north_america shard
        assert {c.city for c in north_american_cities_w_t} == {