- merge default tip

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/sqlalchemy/sql/operators.py b/lib/sqlalchemy/sql/operators.py
index 67830f7cf..0577e6668 100644
--- a/lib/sqlalchemy/sql/operators.py
+++ b/lib/sqlalchemy/sql/operators.py
@@ -83,10 +83,14 @@ def desc_op(a):
 def asc_op(a):
     return a.asc()
 
-_commutative = set([eq, ne, add, mul, and_])
+_commutative = set([eq, ne, add, mul])
+
 def is_commutative(op):
     return op in _commutative
 
+_associative = _commutative.union([concat_op, and_, or_])
+    
+
 _smallest = symbol('_smallest')
 _largest = symbol('_largest')
 
@@ -131,5 +135,8 @@ _PRECEDENCE = {
 }
 
 def is_precedent(operator, against):
-    return (_PRECEDENCE.get(operator, _PRECEDENCE[_smallest]) <=
+    if operator is against and operator in _associative:
+        return False
+    else:
+        return (_PRECEDENCE.get(operator, _PRECEDENCE[_smallest]) <=
             _PRECEDENCE.get(against, _PRECEDENCE[_largest]))