Fix psycopg2 pre_ping with autocommit

Fixed an issue what would cause autocommit mode to be reset
when using pre_ping in conjunction engine level autocommit
on the psycopg2 driver.

Fixes: #7930
Change-Id: I4cccaf1b7f8cbacd853689458080784114fcc390

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py b/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py
index 7f936fefb..e7d5e77c3 100644
--- a/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py
+++ b/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py
@@ -170,15 +170,17 @@ class _PGDialect_common_psycopg(PGDialect):
 
     def do_ping(self, dbapi_connection):
         cursor = None
+        before_autocommit = dbapi_connection.autocommit
         try:
-            self._do_autocommit(dbapi_connection, True)
+            if not before_autocommit:
+                self._do_autocommit(dbapi_connection, True)
             cursor = dbapi_connection.cursor()
             try:
                 cursor.execute(self._dialect_specific_select_one)
             finally:
                 cursor.close()
-                if not dbapi_connection.closed:
-                    self._do_autocommit(dbapi_connection, False)
+                if not before_autocommit and not dbapi_connection.closed:
+                    self._do_autocommit(dbapi_connection, before_autocommit)
         except self.dbapi.Error as err:
             if self.is_disconnect(err, dbapi_connection, cursor):
                 return False