Added defer_except()

CHANGES.rst

@@ -4,7 +4,13 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
-0.1.0 (12.1.2013)
+0.2.0 (2013-03-01)
-^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^
+
+- Added new function defer_except()
+
+
+0.1.0 (2013-01-12)
+^^^^^^^^^^^^^^^^^^
 
 - Initial public release

setup.py

@@ -24,7 +24,7 @@ class PyTest(Command):
 
 setup(
     name='SQLAlchemy-Utils',
-    version='0.1',
+    version='0.2',
     url='https://github.com/kvesteri/sqlalchemy-utils',
     license='BSD',
     author='Konsta Vesterinen',

sqlalchemy_utils/__init__.py

@@ -1,5 +1,7 @@
+from sqlalchemy.orm import defer
 from sqlalchemy.orm.mapper import Mapper
 from sqlalchemy.orm.query import _ColumnEntity
+from sqlalchemy.orm.properties import ColumnProperty
 from sqlalchemy.sql.expression import desc, asc
 
 
@@ -113,6 +115,27 @@ def sort_query(query, sort):
     return query
 
 
+def defer_except(query, columns):
+    """
+    Deferred loads all columns in given query, except the ones given.
+
+        >>> from sqlalchemy_utils import defer_except
+        >>> query = session.query(User)
+        >>> query = defer_except(User, [User.id, User.name])
+
+    :param columns: columns not to deferred load
+    """
+    model = query._entities[0].entity_zero.class_
+    fields = set(model._sa_class_manager.values())
+    for field in fields:
+        property_ = field.property
+        if isinstance(property_, ColumnProperty):
+            column = property_.columns[0]
+            if column.name not in columns:
+                query = query.options(defer(property_.key))
+    return query
+
+
 def escape_like(string, escape_char='*'):
     """
     Escapes the string paremeter used in SQL LIKE expressions