- added a handy multi-use "identity_key()" method to Session, allowing

the generation of identity keys for primary key values, instances,
and rows, courtesy Daniel Miller

diff --git a/CHANGES b/CHANGES
index 18b24cf54087817500e2d65f33f7da6c0eef04d0..bf8a19f8a0da4db16367ced91f9a74d327f0cdaa 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -96,6 +96,10 @@
       worked anyway), but also query.selectfirst(), query.selectone() which
       will be used as is (i.e. no query is compiled). works similarly to
       sending the results to instances().
+
+    - added a handy multi-use "identity_key()" method to Session, allowing
+      the generation of identity keys for primary key values, instances,
+      and rows, courtesy Daniel Miller
       
     - added "refresh-expire" cascade [ticket:492].  allows refresh() and
       expire() calls to propigate along relationships.

diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index a6e1e9ee25a7bfbaca7337c09f28473e5e10689d..c85b356b3e268d7534b36ee7639317ed31b8168d 100644 (file)
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -446,6 +446,54 @@ class Session(object):
             self.save(merged)
         return merged
 
+    def identity_key(self, *args, **kwargs):
+        """Get an identity key
+
+        Valid call signatures:
+
+        identity_key(class_, ident, entity_name=None)
+            class_ - mapped class
+            ident - primary key, if the key is composite this is a tuple
+            entity_name - optional entity name. May be given as a
+                positional arg or as a keyword arg.
+
+        identity_key(instance=instance)
+            instance - object instance (must be given as a keyword arg)
+
+        identity_key(row=row, class=class_, entity_name=None)
+            row - result proxy row (must be given as a keyword arg)
+        """
+        if args:
+            kw = {}
+            if len(args) == 2:
+                class_, ident = args
+                entity_name = kwargs.pop("entity_name", None)
+                assert not kwargs, ("unknown keyword arguments: %s"
+                    % (kwargs.keys(),))
+            else:
+                assert len(args) == 3, ("two or three positional args are "
+                    "accepted, got %s" % len(args))
+                class_, ident, entity_name = args
+            mapper = _class_mapper(class_, entity_name=entity_name)
+            return mapper.instance_key_from_primary_key(ident,
+                entity_name=entity_name)
+        else:
+            try:
+                instance = kwargs.pop("instance")
+            except KeyError:
+                row = kwargs.pop("row")
+                class_ = kwargs.pop("class")
+                entity_name = kwargs.pop("entity_name", None)
+                assert not kwargs, ("unknown keyword arguments: %s"
+                    % (kwargs.keys(),))
+                mapper = _class_mapper(class_, entity_name=entity_name)
+                return mapper.identity_key_from_row(row)
+            else:
+                assert not kwargs, ("unknown keyword arguments: %s"
+                    % (kwargs.keys(),))
+                mapper = _object_mapper(instance)
+                return mapper.identity_key_from_instance(instance)
+
     def _save_impl(self, object, **kwargs):
         if hasattr(object, '_instance_key'):
             if not self.identity_map.has_key(object._instance_key):