- merged with_polymorphic branch, which was merged with query_columns branch

- removes everything to do with select_table, which remains as a keyword argument synonymous with
with_polymorphic=('*', select_table).
- all "polymorphic" selectables find their way to Query by way of _set_select_from() now, so that
all joins/aliasing/eager loads/etc. is handled consistently.  Mapper has methods for producing
polymorphic selectables so that Query and eagerloaders alike can get to them.
- row aliasing simplified, so that they don't need to nest.  they only need the source selectable
and adapt to whatever incoming columns they get.
- Query is more egalitarian about mappers/columns now.  Still has a strong sense of "entity zero",
but also introduces new unpublished/experimental _values() method which sets up a columns-only query.
- Query.order_by() and Query.group_by() take *args now (also still take a list, will likely deprecate
in 0.5).  May want to do this for select() as well.
- the existing "check for False discriminiator" "fix" was not working completely, added coverage
- orphan detection was broken when the target object was a subclass of the mapper with the orphaned
relation, fixed that too.

1 files changed, 12 insertions, 25 deletions

diff --git a/lib/sqlalchemy/sql/visitors.py b/lib/sqlalchemy/sql/visitors.py
index 09d5a0982..7eccc9b89 100644
--- a/lib/sqlalchemy/sql/visitors.py
+++ b/lib/sqlalchemy/sql/visitors.py
@@ -37,17 +37,17 @@ class ClauseVisitor(object):
     traverse_chained = traverse_single
         
     def iterate(self, obj):
-        """traverse the given expression structure, and return an iterator of all elements."""
+        """traverse the given expression structure, returning an iterator of all elements."""
         
         stack = [obj]
-        traversal = []
-        while len(stack) > 0:
+        traversal = util.deque()
+        while stack:
             t = stack.pop()
-            yield t
-            traversal.insert(0, t)
+            traversal.appendleft(t)
             for c in t.get_children(**self.__traverse_options__):
                 stack.append(c)
-    
+        return iter(traversal)
+        
     def traverse(self, obj, clone=False):
         """traverse and visit the given expression structure.
         
@@ -119,32 +119,19 @@ class ClauseVisitor(object):
         def clone(element):
             return self._clone_element(element, stop_on, cloned)
         elem._copy_internals(clone=clone)
-
-        for v in self._iterate_visitors:
-            meth = getattr(v, "visit_%s" % elem.__visit_name__, None)
-            if meth:
-                meth(elem)
+        
+        self.traverse_single(elem)
 
         for e in elem.get_children(**self.__traverse_options__):
             if e not in stop_on:
                 self._cloned_traversal_impl(e, stop_on, cloned)
         return elem
-        
+
     def _non_cloned_traversal(self, obj):
         """a non-recursive, non-cloning traversal."""
-        
-        stack = [obj]
-        traversal = []
-        while len(stack) > 0:
-            t = stack.pop()
-            traversal.insert(0, t)
-            for c in t.get_children(**self.__traverse_options__):
-                stack.append(c)
-        for target in traversal:
-            for v in self._iterate_visitors:
-                meth = getattr(v, "visit_%s" % target.__visit_name__, None)
-                if meth:
-                    meth(target)
+
+        for target in self.iterate(obj):
+            self.traverse_single(target)
         return obj
 
     def _iterate_visitors(self):