- select().as_scalar() will raise an exception if the select does not have

exactly one expression in its columns clause.
- added "helper exception" to select.type access, generic functions raise
the chance of this happening
- a slight behavioral change to attributes is, del'ing an attribute
does *not* cause the lazyloader of that attribute to fire off again;
the "del" makes the effective value of the attribute "None".  To
re-trigger the "loader" for an attribute, use
session.expire(instance, [attrname]).
- fix ormtutorial for IS NULL

1 files changed, 2 insertions, 4 deletions

diff --git a/doc/build/content/ormtutorial.txt b/doc/build/content/ormtutorial.txt
index fbbd3c552..a0382708e 100644
--- a/doc/build/content/ormtutorial.txt
+++ b/doc/build/content/ormtutorial.txt
@@ -807,15 +807,13 @@ A summary of all operators usable on relations:
         [5]
         {stop}[]
 
-    a comparison to `None` also generates a negated EXISTS clause:
+    a comparison to `None` also generates an IS NULL clause for a many-to-one relation:
 
         {python}
         {sql}>>> session.query(Address).filter(Address.user==None).all()
         SELECT addresses.id AS addresses_id, addresses.email_address AS addresses_email_address, addresses.user_id AS addresses_user_id 
         FROM addresses 
-        WHERE NOT (EXISTS (SELECT 1 
-        FROM users 
-        WHERE users.id = addresses.user_id)) ORDER BY addresses.oid
+        WHERE addresses.user_id IS NULL ORDER BY addresses.oid
         []
         {stop}[]