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, 4 insertions, 4 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/pg8000.py b/lib/sqlalchemy/dialects/postgresql/pg8000.py
index 3d1051b7d..d42dd9560 100644
--- a/lib/sqlalchemy/dialects/postgresql/pg8000.py
+++ b/lib/sqlalchemy/dialects/postgresql/pg8000.py
@@ -433,8 +433,8 @@ class PGDialect_pg8000(PGDialect):
         level = level.replace("_", " ")
 
         # adjust for ConnectionFairy possibly being present
-        if hasattr(connection, "connection"):
-            connection = connection.connection
+        if hasattr(connection, "dbapi_connection"):
+            connection = connection.dbapi_connection
 
         if level == "AUTOCOMMIT":
             connection.autocommit = True
@@ -498,8 +498,8 @@ class PGDialect_pg8000(PGDialect):
 
     def set_client_encoding(self, connection, client_encoding):
         # adjust for ConnectionFairy possibly being present
-        if hasattr(connection, "connection"):
-            connection = connection.connection
+        if hasattr(connection, "dbapi_connection"):
+            connection = connection.dbapi_connection
 
         cursor = connection.cursor()
         cursor.execute("SET CLIENT_ENCODING TO '" + client_encoding + "'")