Refs #27683 -- Allowed setting isolation level in DATABASES ['OPTIONS'] on MySQL.

2 files changed, 31 insertions, 0 deletions

diff --git a/docs/ref/databases.txt b/docs/ref/databases.txt
index 16addc52bc..0c2465a9af 100644
--- a/docs/ref/databases.txt
+++ b/docs/ref/databases.txt
@@ -492,6 +492,32 @@ like other MySQL options: either in a config file or with the entry
 ``'init_command': "SET sql_mode='STRICT_TRANS_TABLES'"`` in the
 :setting:`OPTIONS` part of your database configuration in :setting:`DATABASES`.
 
+.. _mysql-isolation-level:
+
+Isolation level
+~~~~~~~~~~~~~~~
+
+.. versionadded:: 1.11
+
+When running concurrent loads, database transactions from different sessions
+(say, separate threads handling different requests) may interact with each
+other. These interactions are affected by each session's `transaction isolation
+level`_. You can set a connection's isolation level with an
+``'isolation_level'`` entry in the :setting:`OPTIONS` part of your database
+configuration in :setting:`DATABASES`. Valid values for
+this entry are the four standard isolation levels:
+
+* ``'read uncommitted'``
+* ``'read committed'``
+* ``'repeatable read'``
+* ``'serializable'``
+
+or ``None`` to use the server's configured isolation level. However, Django
+works best with read committed rather than MySQL's default, repeatable read.
+Data loss is possible with repeatable read.
+
+.. _transaction isolation level: https://dev.mysql.com/doc/refman/en/innodb-transaction-isolation-levels.html
+
 Creating your tables
 --------------------
 
diff --git a/docs/releases/1.11.txt b/docs/releases/1.11.txt
index 08572560ea..1546b68832 100644
--- a/docs/releases/1.11.txt
+++ b/docs/releases/1.11.txt
@@ -255,6 +255,11 @@ Database backends
   the worker memory load (used to hold query results) to the database and might
   increase database memory usage.
 
+* Added MySQL support for the ``'isolation_level'`` option in
+  :setting:`OPTIONS` to allow specifying the :ref:`transaction isolation level
+  <mysql-isolation-level>`. To avoid possible data loss, it's recommended to
+  switch from MySQL's default level, repeatable read, to read committed.
+
 Email
 ~~~~~