Apply minor update to async_orm example

- Fixed import to avoid MovedIn20Warning.

- Separated drop_all() and create_all() into separate
context managers to avoid dropping and creating the
same table within the same transaction. Apparently
some databases (e.g., CockroachDB) don't allow that.

Change-Id: Id26d7d719871a75ffb78c6af589658666802fb2f

1 files changed, 2 insertions, 1 deletions

diff --git a/examples/asyncio/async_orm.py b/examples/asyncio/async_orm.py
index d3355791c..174ebf30b 100644
--- a/examples/asyncio/async_orm.py
+++ b/examples/asyncio/async_orm.py
@@ -13,8 +13,8 @@ from sqlalchemy import Integer
 from sqlalchemy import String
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.ext.asyncio import create_async_engine
-from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.future import select
+from sqlalchemy.orm import declarative_base
 from sqlalchemy.orm import relationship
 from sqlalchemy.orm import selectinload
 from sqlalchemy.orm import sessionmaker
@@ -53,6 +53,7 @@ async def async_main():
 
     async with engine.begin() as conn:
         await conn.run_sync(Base.metadata.drop_all)
+    async with engine.begin() as conn:
         await conn.run_sync(Base.metadata.create_all)
 
     # expire_on_commit=False will prevent attributes from being expired