From: Cedric Brandily <zzelle@gmail.com>
Date: Tue, 3 Nov 2015 21:54:07 +0000 (+0100)
Subject: Optimize delete_csnat_router_interface_ports db query
X-Git-Url: https://review.fuel-infra.org/gitweb?a=commitdiff_plain;h=d5f3d59daf38035ced725be55931cb89ec1ccbcf;p=openstack-build%2Fneutron-build.git

Optimize delete_csnat_router_interface_ports db query

Currently delete_csnat_router_interface_ports provides an iterator as
filter to core_plugin.get_ports which is used in a SQL IN argument.
SQLAlchemy is able to avoid some db queries when the IN argument is
empty BUT not when the argument is an empty iterator and raises the
warning:

 SAWarning: The IN-predicate on "ports.id" was invoked with an empty
 sequence. This results in a contradiction, which nonetheless can be
 expensive to evaluate. Consider alternative strategies for improved
 performance.

This change replaces the iterator by a list in order to optimize db
queries when the filter is empty.

Closes-Bug: #1503852
Change-Id: I4f53433d688dfa020927118a18020b1a6aa55517
---

diff --git a/neutron/db/l3_dvr_db.py b/neutron/db/l3_dvr_db.py
index ba740a068..12df1e4a8 100644
--- a/neutron/db/l3_dvr_db.py
+++ b/neutron/db/l3_dvr_db.py
@@ -660,12 +660,12 @@ class L3_NAT_with_dvr_db_mixin(l3_db.L3_NAT_db_mixin,
 
         # TODO(markmcclain): This is suboptimal but was left to reduce
         # changeset size since it is late in cycle
-        ports = (
+        ports = [
             rp.port.id for rp in
             router.attached_ports.filter_by(
                     port_type=l3_const.DEVICE_OWNER_ROUTER_SNAT)
             if rp.port
-        )
+        ]
 
         c_snat_ports = self._core_plugin.get_ports(
             context,