- The MySQL dialect now renders TIMESTAMP with NULL / NOT NULL in

all cases, so that MySQL 5.6.6 with the
``explicit_defaults_for_timestamp`` flag enabled will
will allow TIMESTAMP to continue to work as expected when
``nullable=False``.  Existing applications are unaffected as
SQLAlchemy has always emitted NULL for a TIMESTAMP column that
is ``nullable=True``.  fixes #3155

2 files changed, 42 insertions, 0 deletions

diff --git a/doc/build/changelog/changelog_10.rst b/doc/build/changelog/changelog_10.rst
index 89ef86844..ca0ae4d52 100644
--- a/doc/build/changelog/changelog_10.rst
+++ b/doc/build/changelog/changelog_10.rst
@@ -1,4 +1,5 @@
 
+
 ==============
 1.0 Changelog
 ==============
@@ -23,6 +24,24 @@
     on compatibility concerns, see :doc:`/changelog/migration_10`.
 
     .. change::
+        :tags: feature, mysql
+        :tickets: 3155
+
+        The MySQL dialect now renders TIMESTAMP with NULL / NOT NULL in
+        all cases, so that MySQL 5.6.6 with the
+        ``explicit_defaults_for_timestamp`` flag enabled will
+        will allow TIMESTAMP to continue to work as expected when
+        ``nullable=False``.  Existing applications are unaffected as
+        SQLAlchemy has always emitted NULL for a TIMESTAMP column that
+        is ``nullable=True``.
+
+        .. seealso::
+
+            :ref:`change_3155`
+
+            :ref:`mysql_timestamp_null`
+
+    .. change::
         :tags: bug, schema
         :tickets: 3299, 3067
 
diff --git a/doc/build/changelog/migration_10.rst b/doc/build/changelog/migration_10.rst
index 3ba0743f7..efb4b26e5 100644
--- a/doc/build/changelog/migration_10.rst
+++ b/doc/build/changelog/migration_10.rst
@@ -1817,6 +1817,29 @@ Support for the pypy psycopg2cffi dialect is added.
 Dialect Improvements and Changes - MySQL
 =============================================
 
+.. _change_3155:
+
+MySQL TIMESTAMP Type now renders NULL / NOT NULL in all cases
+--------------------------------------------------------------
+
+The MySQL dialect has always worked around MySQL's implicit NOT NULL
+default associated with TIMESTAMP columns by emitting NULL for
+such a type, if the column is set up with ``nullable=True``.   However,
+MySQL 5.6.6 and above features a new flag
+`explicit_defaults_for_timestamp <http://dev.mysql.com/doc/refman/
+5.6/en/server-system-variables.html
+#sysvar_explicit_defaults_for_timestamp>`_ which repairs MySQL's non-standard
+behavior to make it behave like any other type; to accommodate this,
+SQLAlchemy now emits NULL/NOT NULL unconditionally for all TIMESTAMP
+columns.
+
+.. seealso::
+
+    :ref:`mysql_timestamp_null`
+
+:ticket:`3155`
+
+
 .. _change_3283:
 
 MySQL SET Type Overhauled to support empty sets, unicode, blank value handling