Allow None to cancel Query.group_by()

This replicates the same behavior as order_by().

order_by() will also be updated to deprecate passing
of False as this is no longer functionally different
than passing None.

Change-Id: I2fc05d0317d28b6c83373769a48f7eea32d56290
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/297

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index c1daaaf07..c5ecbaffe 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -1549,7 +1549,21 @@ class Query(object):
     @_generative(_no_statement_condition, _no_limit_offset)
     def group_by(self, *criterion):
         """apply one or more GROUP BY criterion to the query and return
-        the newly resulting :class:`.Query`"""
+        the newly resulting :class:`.Query`
+
+        All existing GROUP BY settings can be suppressed by
+        passing ``None`` - this will suppress any GROUP BY configured
+        on mappers as well.
+
+        .. versionadded:: 1.1 GROUP BY can be cancelled by passing None,
+           in the same way as ORDER BY.
+
+        """
+
+        if len(criterion) == 1:
+            if criterion[0] is None:
+                self._group_by = False
+                return
 
         criterion = list(chain(*[_orm_columns(c) for c in criterion]))
         criterion = self._adapt_col_list(criterion)