- further fixes for #3347; track the mappers we're joining

between fully and match on those, rather than trying to
compare selectables; fixes #3347

1 files changed, 29 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index ad071376d..b3f3bc5fa 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -776,7 +776,10 @@ class _ORMJoin(expression.Join):
 
     __visit_name__ = expression.Join.__visit_name__
 
-    def __init__(self, left, right, onclause=None, isouter=False):
+    def __init__(
+            self,
+            left, right, onclause=None, isouter=False,
+            _left_memo=None, _right_memo=None):
 
         left_info = inspection.inspect(left)
         left_orm_info = getattr(left, '_joined_from_info', left_info)
@@ -786,6 +789,9 @@ class _ORMJoin(expression.Join):
 
         self._joined_from_info = right_info
 
+        self._left_memo = _left_memo
+        self._right_memo = _right_memo
+
         if isinstance(onclause, util.string_types):
             onclause = getattr(left_orm_info.entity, onclause)
 
@@ -837,6 +843,28 @@ class _ORMJoin(expression.Join):
                 single_crit = right_info._adapter.traverse(single_crit)
             self.onclause = self.onclause & single_crit
 
+    def _splice_into_center(self, other):
+        """Splice a join into the center.
+
+        Given join(a, b) and join(b, c), return join(a, b).join(c)
+
+        """
+        assert self.right is other.left
+
+        left = _ORMJoin(
+            self.left, other.left,
+            self.onclause, isouter=self.isouter,
+            _left_memo=self._left_memo,
+            _right_memo=other._left_memo
+        )
+
+        return _ORMJoin(
+            left,
+            other.right,
+            other.onclause, isouter=other.isouter,
+            _right_memo=other._right_memo
+        )
+
     def join(self, right, onclause=None, isouter=False, join_to_left=None):
         return _ORMJoin(self, right, onclause, isouter)