Don't include SelectBase when searching for surface column elements

Fixed bug where correlated select used against single-table inheritance
entity would fail to render correctly in the outer query, due to adjustment
for single inheritance discriminator criteria inappropriately re-applying
the criteria to the outer query.

Change-Id: I38df21f1392af1843e10119682fa0635d346e2a8
Fixes: #4103

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/util.py b/lib/sqlalchemy/sql/util.py
index 281d5f6a3..0c122949b 100644
--- a/lib/sqlalchemy/sql/util.py
+++ b/lib/sqlalchemy/sql/util.py
@@ -18,7 +18,7 @@ from collections import deque
 from .elements import BindParameter, ColumnClause, ColumnElement, \
     Null, UnaryExpression, literal_column, Label, _label_reference, \
     _textual_label_reference
-from .selectable import ScalarSelect, Join, FromClause, FromGrouping
+from .selectable import SelectBase, ScalarSelect, Join, FromClause, FromGrouping
 from .schema import Column
 
 join_condition = util.langhelpers.public_factory(
@@ -235,17 +235,21 @@ def surface_selectables(clause):
             stack.append(elem.element)
 
 
-def surface_column_elements(clause):
+def surface_column_elements(clause, include_scalar_selects=True):
     """traverse and yield only outer-exposed column elements, such as would
     be addressable in the WHERE clause of a SELECT if this element were
     in the columns clause."""
 
+    filter_ = (FromGrouping, )
+    if not include_scalar_selects:
+        filter_ += (SelectBase, )
+
     stack = deque([clause])
     while stack:
         elem = stack.popleft()
         yield elem
         for sub in elem.get_children():
-            if isinstance(sub, FromGrouping):
+            if isinstance(sub, filter_):
                 continue
             stack.append(sub)