- Behavioral improvement: empty

    conjunctions such as and_() and or_() will be
    flattened in the context of an enclosing conjunction,
    i.e. and_(x, or_()) will produce 'X' and not 'X AND
    ()'. [ticket:2257].

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index 082313724..9e920c34f 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -2902,6 +2902,12 @@ class BooleanClauseList(ClauseList, ColumnElement):
     def _select_iterable(self):
         return (self, )
 
+    def self_group(self, against=None):
+        if not self.clauses:
+            return self
+        else:
+            return super(BooleanClauseList, self).self_group(against=against)
+
 class _Tuple(ClauseList, ColumnElement):
 
     def __init__(self, *clauses, **kw):