improved translation of rows when proxying rows from one mapper to another.

2 files changed, 20 insertions, 11 deletions

diff --git a/examples/polymorph/polymorph2.py b/examples/polymorph/polymorph2.py
index eebac80c1..fb9504fbe 100644
--- a/examples/polymorph/polymorph2.py
+++ b/examples/polymorph/polymorph2.py
@@ -73,7 +73,8 @@ person_join = select(
                     column("'engineer'").label('type')
                 ],
             people.c.person_id==engineers.c.person_id)).alias('pjoin')
-            
+
+print [c for c in person_join.c]            
     
 # MapperExtension object.
 class PersonLoader(MapperExtension):
@@ -87,10 +88,10 @@ class PersonLoader(MapperExtension):
             
     def populate_instance(self, mapper, instance, row, identitykey, imap, isnew):
         if row[person_join.c.type] =='engineer':
-            Engineer.mapper.populate_instance(instance, row, identitykey, imap, isnew)
+            Engineer.mapper.populate_instance(instance, row, identitykey, imap, isnew, frommapper=mapper)
             return False
         elif row[person_join.c.type] =='manager':
-            Manager.mapper.populate_instance(instance, row, identitykey, imap, isnew)
+            Manager.mapper.populate_instance(instance, row, identitykey, imap, isnew, frommapper=mapper)
             return False
         else:
             return True
diff --git a/lib/sqlalchemy/mapping/mapper.py b/lib/sqlalchemy/mapping/mapper.py
index 32da013ac..82257ae62 100644
--- a/lib/sqlalchemy/mapping/mapper.py
+++ b/lib/sqlalchemy/mapping/mapper.py
@@ -854,19 +854,27 @@ class Mapper(object):
         # call further mapper properties on the row, to pull further 
         # instances from the row and possibly populate this item.
         if self.extension.populate_instance(self, instance, row, identitykey, imap, isnew):
-            self.populate_instance(instance, row, identitykey, imap, isnew, translate=False)
+            self.populate_instance(instance, row, identitykey, imap, isnew)
         if self.extension.append_result(self, row, imap, result, instance, isnew, populate_existing=populate_existing):
             if result is not None:
                 result.append_nohistory(instance)
         return instance
 
-    def populate_instance(self, instance, row, identitykey, imap, isnew, translate=True):
-        if translate:
-            newrow = {}
-            for table in self.tables:
-                for c in table.c:
-                    newrow[c] = row[c.key]
-            row = newrow
+    def translate_row(self, tomapper, row):
+        """attempts to take a row and translate its values to a row that can
+        be understood by another mapper.  breaks the column references down to their
+        bare keynames to accomplish this.  So far this works for the various polymorphic
+        examples."""
+        newrow = util.DictDecorator(row)
+        for c in self.table.c:
+            newrow[c.key] = row[c]
+        for c in tomapper.table.c:
+            newrow[c] = newrow[c.key]
+        return newrow
+        
+    def populate_instance(self, instance, row, identitykey, imap, isnew, frommapper=None):
+        if frommapper is not None:
+            row = frommapper.translate_row(self, row)
             
         for prop in self.props.values():
             prop.execute(instance, row, identitykey, imap, isnew)