Surface driver connection object when using a proxied dialect

Improve the interface used by adapted drivers, like the asyncio ones,
to access the actual connection object returned by the driver.

The :class:`_engine._ConnectionRecord` and
:class:`_engine._ConnectionFairy` now have two new attributes:

* ``dbapi_connection`` always represents a DBAPI compatible
object.  For pep-249 drivers, this is the DBAPI connection as it always
has been, previously accessed under the ``.connection`` attribute.
For asyncio drivers that SQLAlchemy adapts into a pep-249 interface,
the returned object will normally be a SQLAlchemy adaption object
called :class:`_engine.AdaptedConnection`.
* ``driver_connection`` always represents the actual connection object
maintained by the third party pep-249 DBAPI or async driver in use.
For standard pep-249 DBAPIs, this will always be the same object
as that of the ``dbapi_connection``.  For an asyncio driver, it will be
the underlying asyncio-only connection object.

The ``.connection`` attribute remains available and is now a legacy alias
of ``.dbapi_connection``.

Fixes: #6832
Change-Id: Ib72f97deefca96dce4e61e7c38ba430068d6a82e

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/aiomysql.py b/lib/sqlalchemy/dialects/mysql/aiomysql.py
index c9a87145e..c5ba635c2 100644
--- a/lib/sqlalchemy/dialects/mysql/aiomysql.py
+++ b/lib/sqlalchemy/dialects/mysql/aiomysql.py
@@ -13,7 +13,7 @@ r"""
 
 .. warning:: The aiomysql dialect as of September, 2021 appears to be unmaintained
    and no longer functions for Python version 3.10.   Please refer to the
-   :ref:`asyncmy` dialect for current MySQL asyncio functionality.
+   :ref:`asyncmy` dialect for current MySQL/MariaDD asyncio functionality.
 
 The aiomysql dialect is SQLAlchemy's second Python asyncio dialect.
 
@@ -33,6 +33,7 @@ This dialect should normally be used only with the
 from .pymysql import MySQLDialect_pymysql
 from ... import pool
 from ... import util
+from ...engine import AdaptedConnection
 from ...util.concurrency import asyncio
 from ...util.concurrency import await_fallback
 from ...util.concurrency import await_only
@@ -173,7 +174,7 @@ class AsyncAdapt_aiomysql_ss_cursor(AsyncAdapt_aiomysql_cursor):
         return self.await_(self._cursor.fetchall())
 
 
-class AsyncAdapt_aiomysql_connection:
+class AsyncAdapt_aiomysql_connection(AdaptedConnection):
     await_ = staticmethod(await_only)
     __slots__ = ("dbapi", "_connection", "_execute_mutex")
 
@@ -306,5 +307,8 @@ class MySQLDialect_aiomysql(MySQLDialect_pymysql):
 
         return CLIENT.FOUND_ROWS
 
+    def get_driver_connection(self, connection):
+        return connection._connection
+
 
 dialect = MySQLDialect_aiomysql