- pick around gaining modest dings in callcounts here and there

2 files changed, 16 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index 3384939b0..42d2e4e12 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -43,9 +43,10 @@ def _interpret_as_from(element):
                 {"expr": util.ellipses_string(element)})
 
             return TextClause(util.text_type(element))
-    elif hasattr(insp, "selectable"):
+    try:
         return insp.selectable
-    raise exc.ArgumentError("FROM expression expected")
+    except AttributeError:
+        raise exc.ArgumentError("FROM expression expected")
 
 
 def _interpret_as_select(element):
diff --git a/lib/sqlalchemy/sql/visitors.py b/lib/sqlalchemy/sql/visitors.py
index d09b82148..b53b44eec 100644
--- a/lib/sqlalchemy/sql/visitors.py
+++ b/lib/sqlalchemy/sql/visitors.py
@@ -213,12 +213,19 @@ def iterate(obj, opts):
     traversal is configured to be breadth-first.
 
     """
+    # fasttrack for atomic elements like columns
+    children = obj.get_children(**opts)
+    if not children:
+        return [obj]
+
+    traversal = deque()
     stack = deque([obj])
     while stack:
         t = stack.popleft()
-        yield t
+        traversal.append(t)
         for c in t.get_children(**opts):
             stack.append(c)
+    return iter(traversal)
 
 
 def iterate_depthfirst(obj, opts):
@@ -227,6 +234,11 @@ def iterate_depthfirst(obj, opts):
     traversal is configured to be depth-first.
 
     """
+    # fasttrack for atomic elements like columns
+    children = obj.get_children(**opts)
+    if not children:
+        return [obj]
+
     stack = deque([obj])
     traversal = deque()
     while stack: