From a233638268d5991ec1f4f928104a041e607bb4fc Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sun, 16 Jan 2011 13:15:26 -0500
Subject: [PATCH] - add dialect.reset_isolation_level(), reverts - base not
 implemented methods on Dialect

---
 lib/sqlalchemy/engine/base.py    | 15 +++++++++++++++
 lib/sqlalchemy/engine/default.py | 11 +++++++++++
 test/engine/test_transaction.py  | 29 +++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 9eb1b8b400..1727e6905a 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -524,6 +524,21 @@ class Dialect(object):
         """
         return None
 
+    def reset_isolation_level(self, dbapi_conn):
+        """Given a DBAPI connection, revert its isolation to the default."""
+
+        raise NotImplementedError()
+
+    def set_isolation_level(self, dbapi_conn, level):
+        """Given a DBAPI connection, set its isolation level."""
+
+        raise NotImplementedError()
+
+    def get_isolation_level(self, dbapi_conn):
+        """Given a DBAPI connection, return its isolation level."""
+
+        raise NotImplementedError()
+
 
 class ExecutionContext(object):
     """A messenger object for a Dialect that corresponds to a single
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index da6ed12a6d..30a53bb203 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -175,6 +175,12 @@ class DefaultDialect(base.Dialect):
         except NotImplementedError:
             self.default_schema_name = None
 
+        try:
+            self.default_isolation_level = \
+                        self.get_isolation_level(connection.connection)
+        except NotImplementedError:
+            self.default_isolation_level = None
+
         self.returns_unicode_strings = self._check_unicode_returns(connection)
 
         self.do_rollback(connection.connection)
@@ -320,6 +326,11 @@ class DefaultDialect(base.Dialect):
     def is_disconnect(self, e):
         return False
 
+    def reset_isolation_level(self, dbapi_conn):
+        self.set_isolation_level(dbapi_conn, 
+                    self.isolation_level or self.default_isolation_level)
+
+
 
 class DefaultExecutionContext(base.ExecutionContext):
     isinsert = False
diff --git a/test/engine/test_transaction.py b/test/engine/test_transaction.py
index 1fb0267bb5..6878fea39f 100644
--- a/test/engine/test_transaction.py
+++ b/test/engine/test_transaction.py
@@ -1163,6 +1163,35 @@ class IsolationLevelTest(TestBase):
         isolation_level = eng.dialect.get_isolation_level(eng.connect().connection)
         eq_(isolation_level, self._default_isolation_level())
 
+    @testing.requires.isolation_level
+    def test_reset_level(self):
+        eng = create_engine(testing.db.url)
+        conn = eng.connect()
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._default_isolation_level())
+
+        eng.dialect.set_isolation_level(conn.connection, self._non_default_isolation_level())
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._non_default_isolation_level())
+
+        eng.dialect.reset_isolation_level(conn.connection)
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._default_isolation_level())
+
+        conn.close()
+
+    @testing.requires.isolation_level
+    def test_reset_level_with_setting(self):
+        eng = create_engine(testing.db.url, isolation_level=self._non_default_isolation_level())
+        conn = eng.connect()
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._non_default_isolation_level())
+
+        eng.dialect.set_isolation_level(conn.connection, self._default_isolation_level())
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._default_isolation_level())
+
+        eng.dialect.reset_isolation_level(conn.connection)
+        eq_(eng.dialect.get_isolation_level(conn.connection), self._non_default_isolation_level())
+
+        conn.close()
+
+
     @testing.requires.isolation_level
     def test_invalid_level(self):
         eng = create_engine(testing.db.url, isolation_level='FOO')
-- 
2.47.2