From ef6b9a0c72a0e47d7345286911a3d882ee1f1909 Mon Sep 17 00:00:00 2001
From: Goutham Pacha Ravi <gouthampravi@gmail.com>
Date: Tue, 11 Feb 2020 17:04:44 -0800
Subject: [PATCH] Fix database loading for some resources

Whenever we use share network subnets, we'd
always need the associated share networks; so
'joined' loading them makes sense rather than
lazy loading. Same is true for Share Group
Snapshots, since share group attributes are
relevant in contexts that snapshots are
referenced.

Fix the ORM relationship loading technique
and queries appropriately. Also convert share
network name into a property of the share
network subnet class.

Co-Authored-By: Carlos Eduardo <ces.eduardo98@gmail.com>
Closes-Bug: #1862833
Change-Id: I8c29760479f9c874d618e2c15ebab75bffeb3cbb
---
 manila/api/views/share_network_subnets.py              |  2 +-
 manila/db/sqlalchemy/api.py                            |  5 +++--
 manila/db/sqlalchemy/models.py                         | 10 ++++++++--
 ...-fix-backref-by-eager-loading-2d897976e7598625.yaml |  5 +++++
 4 files changed, 17 insertions(+), 5 deletions(-)
 create mode 100644 releasenotes/notes/bug-1862833-fix-backref-by-eager-loading-2d897976e7598625.yaml

diff --git a/manila/api/views/share_network_subnets.py b/manila/api/views/share_network_subnets.py
index 64e0d62b99..342ff2bec0 100644
--- a/manila/api/views/share_network_subnets.py
+++ b/manila/api/views/share_network_subnets.py
@@ -37,7 +37,7 @@ class ViewBuilder(common.ViewBuilder):
             'id': share_network_subnet.get('id'),
             'availability_zone': share_network_subnet.get('availability_zone'),
             'share_network_id': share_network_subnet.get('share_network_id'),
-            'share_network_name': share_network_subnet.share_network['name'],
+            'share_network_name': share_network_subnet['share_network_name'],
             'created_at': share_network_subnet.get('created_at'),
             'segmentation_id': share_network_subnet.get('segmentation_id'),
             'neutron_subnet_id': share_network_subnet.get('neutron_subnet_id'),
diff --git a/manila/db/sqlalchemy/api.py b/manila/db/sqlalchemy/api.py
index 312b21c450..32cc8ac134 100644
--- a/manila/db/sqlalchemy/api.py
+++ b/manila/db/sqlalchemy/api.py
@@ -43,6 +43,7 @@ import six
 from sqlalchemy import MetaData
 from sqlalchemy import or_
 from sqlalchemy.orm import joinedload
+from sqlalchemy.orm import subqueryload
 from sqlalchemy.sql.expression import literal
 from sqlalchemy.sql.expression import true
 from sqlalchemy.sql import func
@@ -3400,7 +3401,7 @@ def _network_get_query(context, session=None):
     return (model_query(context, models.ShareNetwork, session=session).
             options(joinedload('share_instances'),
                     joinedload('security_services'),
-                    joinedload('share_network_subnets')))
+                    subqueryload('share_network_subnets')))
 
 
 @require_context
@@ -3543,7 +3544,7 @@ def _network_subnet_get_query(context, session=None):
     if session is None:
         session = get_session()
     return (model_query(context, models.ShareNetworkSubnet, session=session).
-            options(joinedload('share_servers')))
+            options(joinedload('share_servers'), joinedload('share_network')))
 
 
 @require_context
diff --git a/manila/db/sqlalchemy/models.py b/manila/db/sqlalchemy/models.py
index f1c0f97471..8b7fcb0206 100644
--- a/manila/db/sqlalchemy/models.py
+++ b/manila/db/sqlalchemy/models.py
@@ -938,7 +938,9 @@ class ShareNetwork(BASE, ManilaBase):
                     'ShareNetwork.id == ShareInstance.share_network_id,'
                     'ShareInstance.deleted == "False")')
     share_network_subnets = orm.relationship(
-        "ShareNetworkSubnet", backref='share_network', lazy='immediate',
+        "ShareNetworkSubnet",
+        lazy='joined',
+        backref=orm.backref('share_network', lazy='joined'),
         primaryjoin='and_'
                     '(ShareNetwork.id == ShareNetworkSubnet.share_network_id,'
                     'ShareNetworkSubnet.deleted == "False")')
@@ -990,6 +992,10 @@ class ShareNetworkSubnet(BASE, ManilaBase):
     def is_default(self):
         return self.availability_zone_id is None
 
+    @property
+    def share_network_name(self):
+        return self.share_network['name']
+
 
 class ShareServer(BASE, ManilaBase):
     """Represents share server used by share."""
@@ -1216,7 +1222,7 @@ class ShareGroupSnapshot(BASE, ManilaBase):
     status = Column(String(255))
     share_group = orm.relationship(
         ShareGroup,
-        backref="snapshots",
+        backref=orm.backref("snapshots", lazy='joined'),
         foreign_keys=share_group_id,
         primaryjoin=('and_('
                      'ShareGroupSnapshot.share_group_id == ShareGroup.id,'
diff --git a/releasenotes/notes/bug-1862833-fix-backref-by-eager-loading-2d897976e7598625.yaml b/releasenotes/notes/bug-1862833-fix-backref-by-eager-loading-2d897976e7598625.yaml
new file mode 100644
index 0000000000..1e3cacf8be
--- /dev/null
+++ b/releasenotes/notes/bug-1862833-fix-backref-by-eager-loading-2d897976e7598625.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Some resources will be eagerly loaded from the database to avoid cyclical
+    references and faulty results if their retrieval is deferred.