- A warning is emitted if the ``isolation_level`` parameter is used

with :meth:`.Connection.execution_options` when a :class:`.Transaction`
is in play; DBAPIs and/or SQLAlchemy dialects such as psycopg2,
MySQLdb may implicitly rollback or commit the transaction, or
not change the setting til next transaction, so this is never safe.
- Added new parameter :paramref:`.Session.connection.execution_options`
which may be used to set up execution options on a :class:`.Connection`
when it is first checked out, before the transaction has begun.
This is used to set up options such as isolation level on the
connection before the transaction starts.
- added new documentation section
detailing best practices for setting transaction isolation with
sessions.
fixes #3296

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/__init__.py b/lib/sqlalchemy/engine/__init__.py
index f512e260a..7a14cdfb5 100644
--- a/lib/sqlalchemy/engine/__init__.py
+++ b/lib/sqlalchemy/engine/__init__.py
@@ -275,6 +275,8 @@ def create_engine(*args, **kwargs):
 
             :ref:`MySQL Transaction Isolation <mysql_isolation_level>`
 
+            :ref:`session_transaction_isolation` - for the ORM
+
     :param label_length=None: optional integer value which limits
         the size of dynamically generated column labels to that many
         characters. If less than 6, labels are generated as