From: AKamyshnikova <akamyshnikova@mirantis.com>
Date: Tue, 6 Oct 2015 08:23:11 +0000 (+0300)
Subject: Add note in database section of 'effective neutron'
X-Git-Url: https://review.fuel-infra.org/gitweb?a=commitdiff_plain;h=fa4fbcf5b584a0bb1c1f9df2fa1adb455669d428;p=openstack-build%2Fneutron-build.git

Add note in database section of 'effective neutron'

Add note about usage aggregate functions with GROUP BY for
PostgreSQL.

Change-Id: I50af8e8e19f638f774d0f1cfb30f56f6cecad65e
---

diff --git a/doc/source/devref/effective_neutron.rst b/doc/source/devref/effective_neutron.rst
index 4cbea6e6f..bdca1e3ce 100644
--- a/doc/source/devref/effective_neutron.rst
+++ b/doc/source/devref/effective_neutron.rst
@@ -63,7 +63,22 @@ Document common pitfalls as well as good practices done during database developm
   does not raise an exception.
 * Do not get an object to delete it. If you can `delete() <http://docs.sqlalchemy.org/en/rel_1_0/orm/query.html#sqlalchemy.orm.query.Query.delete>`_
   on the query object. Read the warnings for more details about in-python cascades.
-* ...
+* For PostgreSQL if you're using GROUP BY everything in the SELECT list must be
+  an aggregate SUM(...), COUNT(...), etc or used in the GROUP BY.
+
+  The incorrect variant:
+
+  .. code:: python
+
+     q = query(Object.id, Object.name,
+               func.count(Object.number)).group_by(Object.name)
+
+  The correct variant:
+
+  .. code:: python
+
+     q = query(Object.id, Object.name,
+               func.count(Object.number)).group_by(Object.id, Object.name)
 
 System development
 ~~~~~~~~~~~~~~~~~~