- tightened down conditions used to locate "relation direction", associating

  the "foreignkey" of the relationship with the "primaryjoin".  the column match now
  must be exact, not just "corresponding".  this enables self-referential relationships on a
  polymorphic mapper.
  - a little bit of improvement to the concept of a "concrete" inheritance mapping, though that concept
  is not well fleshed out yet (added test case to support concrete mappers on top of a polymorphic base).

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql.py b/lib/sqlalchemy/sql.py
index f944b468d..5b960546e 100644
--- a/lib/sqlalchemy/sql.py
+++ b/lib/sqlalchemy/sql.py
@@ -728,9 +728,17 @@ class FromClause(Selectable):
         if not hasattr(self, '_oid_column'):
             self._oid_column = self._locate_oid_column()
         return self._oid_column
-    def corresponding_column(self, column, raiseerr=True, keys_ok=False):
+    def corresponding_column(self, column, raiseerr=True, keys_ok=False, require_exact=False):
         """given a ColumnElement, return the ColumnElement object from this 
         Selectable which corresponds to that original Column via a proxy relationship."""
+        if require_exact:
+            if self.columns.get(column.key) is column:
+                return column
+            else:
+                if not raiseerr:
+                    return None
+                else:
+                    raise exceptions.InvalidRequestError("Column instance '%s' is not directly present in table '%s'" % (str(column), str(column.table)))
         for c in column.orig_set:
             try:
                 return self.original_columns[c]