added defer and undefer mapper options

2 files changed, 27 insertions, 2 deletions

diff --git a/lib/sqlalchemy/mapping/__init__.py b/lib/sqlalchemy/mapping/__init__.py
index 3217e283e..f5d635213 100644
--- a/lib/sqlalchemy/mapping/__init__.py
+++ b/lib/sqlalchemy/mapping/__init__.py
@@ -29,6 +29,7 @@ from properties import *
 import mapper as mapperlib
 
 __all__ = ['relation', 'eagerload', 'lazyload', 'noload', 'deferred', 'assignmapper', 'column', 'deferred',
+        'defer', 'undefer',
         'mapper', 'clear_mappers', 'objectstore', 'sql', 'extension', 'class_mapper', 'object_mapper', 'MapperExtension',
         'ColumnProperty', 'assign_mapper'
         ]
@@ -137,6 +138,15 @@ def noload(name, **kwargs):
     """returns a MapperOption that will convert the property of the given name
     into a non-load.  Used with mapper.options()"""
     return EagerLazyOption(name, toeager=None, **kwargs)
+
+def defer(name, **kwargs):
+    """returns a MapperOption that will convert the column property of the given 
+    name into a deferred load.  Used with mapper.options()"""
+    return DeferredOption(name, defer=True)
+def undefer(name, **kwargs):
+    """returns a MapperOption that will convert the column property of the given
+    name into a non-deferred (regular column) load.  Used with mapper.options."""
+    return DeferredOption(name, defer=False)
     
 def object_mapper(object):
     """given an object, returns the primary Mapper associated with the object
diff --git a/lib/sqlalchemy/mapping/properties.py b/lib/sqlalchemy/mapping/properties.py
index 41236261e..b7b59508e 100644
--- a/lib/sqlalchemy/mapping/properties.py
+++ b/lib/sqlalchemy/mapping/properties.py
@@ -87,7 +87,7 @@ class DeferredColumnProperty(ColumnProperty):
             
             if self.group is not None:
                 groupcols = [p for p in self.parent.props.values() if isinstance(p, DeferredColumnProperty) and p.group==self.group]
-                row = sql.select([g.columns[0] for g in groupcols], clause).execute().fetchone()
+                row = sql.select([g.columns[0] for g in groupcols], clause, use_labels=True).execute().fetchone()
                 for prop in groupcols:
                     if prop is self:
                         continue
@@ -95,7 +95,7 @@ class DeferredColumnProperty(ColumnProperty):
                     objectstore.global_attributes.create_history(instance, prop.key, uselist=False)
                 return row[self.columns[0]]    
             else:
-                return sql.select([self.columns[0]], clause).scalar()
+                return sql.select([self.columns[0]], clause, use_labels=True).scalar()
         return lazyload
 
     def _is_primary(self):
@@ -819,6 +819,21 @@ class EagerLazyOption(GenericOption):
         kwargs = util.constructor_args(mapper.props[key], **self.kwargs)
         mapper.set_property(key, class_(**kwargs ))
 
+class DeferredOption(GenericOption):
+    def __init__(self, key, defer=False, **kwargs):
+        self.key = key
+        self.defer = defer
+        self.kwargs = kwargs
+    def hash_key(self):
+        return "DeferredOption(%s,%s)" % (self.key, self.defer)
+    def create_prop(self, mapper, key):
+        oldprop = mapper.props[key]
+        if self.defer:
+            prop = DeferredColumnProperty(*oldprop.columns, **self.kwargs)
+        else:
+            prop = ColumnProperty(*oldprop.columns, **self.kwargs)
+        mapper.set_property(key, prop)
+        
 class Aliasizer(sql.ClauseVisitor):
     """converts a table instance within an expression to be an alias of that table."""
     def __init__(self, *tables, **kwargs):