convert AsyncSession.delete into awaitable

The API for :meth:`_asyncio.AsyncSession.delete` is now an awaitable;
this method cascades along relationships which must be loaded in a
similar manner as the :meth:`_asyncio.AsyncSession.merge` method.

Fixes: #5998
Change-Id: Iae001efe99a1dcc47598b4a2491d17c4157fbbfa

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/sqlalchemy/ext/asyncio/session.py b/lib/sqlalchemy/ext/asyncio/session.py
index faa279cf9..93af178a3 100644
--- a/lib/sqlalchemy/ext/asyncio/session.py
+++ b/lib/sqlalchemy/ext/asyncio/session.py
@@ -28,7 +28,6 @@ T = TypeVar("T")
         "__iter__",
         "add",
         "add_all",
-        "delete",
         "expire",
         "expire_all",
         "expunge",
@@ -223,6 +222,18 @@ class AsyncSession:
         )
         return _result.AsyncResult(result)
 
+    async def delete(self, instance):
+        """Mark an instance as deleted.
+
+        The database delete operation occurs upon ``flush()``.
+
+        As this operation may need to cascade along unloaded relationships,
+        it is awaitable to allow for those queries to take place.
+
+
+        """
+        return await greenlet_spawn(self.sync_session.delete, instance)
+
     async def merge(self, instance, load=True):
         """Copy the state of a given instance into a corresponding instance
         within this :class:`_asyncio.AsyncSession`.