here's the flat join thing. it just works. Changing the existing compiled SQL assertions

might even be most of the tests we need (though dedicated sql tests would be needed anyway)

3 files changed, 19 insertions, 8 deletions

diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py
index cabfb35b9..baaf4cb92 100644
--- a/lib/sqlalchemy/orm/strategies.py
+++ b/lib/sqlalchemy/orm/strategies.py
@@ -1089,7 +1089,8 @@ class JoinedLoader(AbstractRelationshipLoader):
             to_adapt = with_poly_info.entity
         else:
             to_adapt = orm_util.AliasedClass(self.mapper,
-                                use_mapper_path=True)
+                                use_mapper_path=True,
+                                flat=True)
         clauses = orm_util.ORMAdapter(
                     to_adapt,
                     equivalents=self.mapper._equivalent_columns,
diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index bd8228f2c..3da6e89e3 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -493,6 +493,7 @@ class AliasedClass(object):
     """
     def __init__(self, cls, alias=None,
                             name=None,
+                            flat=False,
                             adapt_on_names=False,
                             #  TODO: None for default here?
                             with_polymorphic_mappers=(),
@@ -501,7 +502,7 @@ class AliasedClass(object):
                             use_mapper_path=False):
         mapper = _class_to_mapper(cls)
         if alias is None:
-            alias = mapper._with_polymorphic_selectable.alias(name=name)
+            alias = mapper._with_polymorphic_selectable.alias(name=name, flat=flat)
         self._aliased_insp = AliasedInsp(
             self,
             mapper,
@@ -837,7 +838,7 @@ def with_polymorphic(base, classes, selectable=False,
                     _with_polymorphic_args(classes, selectable,
                                 innerjoin=innerjoin)
     if aliased:
-        selectable = selectable.alias()
+        selectable = selectable.alias(flat=True)
     return AliasedClass(base,
                 selectable,
                 with_polymorphic_mappers=mappers,
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index edab9e290..633a3ddba 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -795,7 +795,7 @@ def intersect_all(*selects, **kwargs):
     return CompoundSelect(CompoundSelect.INTERSECT_ALL, *selects, **kwargs)
 
 
-def alias(selectable, name=None):
+def alias(selectable, name=None, flat=False):
     """Return an :class:`.Alias` object.
 
     An :class:`.Alias` represents any :class:`.FromClause`
@@ -2634,7 +2634,7 @@ class FromClause(Selectable):
 
         return Join(self, right, onclause, True)
 
-    def alias(self, name=None):
+    def alias(self, name=None, flat=False):
         """return an alias of this :class:`.FromClause`.
 
         This is shorthand for calling::
@@ -3971,7 +3971,7 @@ class Join(FromClause):
     def bind(self):
         return self.left.bind or self.right.bind
 
-    def alias(self, name=None):
+    def alias(self, name=None, flat=False):
         """return an alias of this :class:`.Join`.
 
         Used against a :class:`.Join` object,
@@ -3999,7 +3999,16 @@ class Join(FromClause):
         aliases.
 
         """
-        return self.select(use_labels=True, correlate=False).alias(name)
+        if flat:
+            assert name is None, "Can't send name argument with flat"
+            left_a, right_a = self.left.alias(), self.right.alias()
+            adapter = sqlutil.ClauseAdapter(left_a).\
+                        chain(sqlutil.ClauseAdapter(right_a))
+
+            return left_a.join(right_a,
+                        adapter.traverse(self.onclause), isouter=self.isouter)
+        else:
+            return self.select(use_labels=True, correlate=False).alias(name)
 
     @property
     def _hide_froms(self):
@@ -4129,7 +4138,7 @@ class CTE(Alias):
         self._restates = _restates
         super(CTE, self).__init__(selectable, name=name)
 
-    def alias(self, name=None):
+    def alias(self, name=None, flat=False):
         return CTE(
             self.original,
             name=name,