removed not-always-applicable check for "polymorphic_identity"

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 18c4c3acb818a5cf3eae50588026761e877de1ad..4a46cc7d87946c4ab4dd71175fe92b0607058481 100644 (file)
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -518,8 +518,6 @@ class Mapper(object):
         or through proxying relationships. Currently, non-column properties are *not* copied.  this implies
         that a polymorphic mapper cant do any eager loading right now."""
         if self.select_table is not self.mapped_table:
-            if self.polymorphic_identity is None:
-                raise exceptions.ArgumentError("Could not locate a polymorphic_identity field for mapper '%s'.  This field is required for polymorphic mappers" % str(self))
             props = {}
             if self.properties is not None:
                 for key, prop in self.properties.iteritems():