From f8b71b604c6dfc6ddd779bc3ce0059f6f8f24505 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aur=C3=A9lien=20Delobelle?= <aurelien.delobelle@gmail.com>
Date: Thu, 6 Apr 2017 18:42:00 +0200
Subject: [PATCH] Fewer db accesses on transfers list view.

- Add select_related for `from_acc`, `to_acc` and `group.valid_by`.
- 2 requests instead of (3 * #transfers)
---
 kfet/views.py | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/kfet/views.py b/kfet/views.py
index ebe169ca..c296d3b3 100644
--- a/kfet/views.py
+++ b/kfet/views.py
@@ -1477,19 +1477,32 @@ class SettingsUpdate(SuccessMessageMixin, UpdateView):
         Settings.empty_cache()
         return super(SettingsUpdate, self).form_valid(form)
 
+
 # -----
 # Transfer views
 # -----
 
 @teamkfet_required
 def transfers(request):
-    transfergroups = (TransferGroup.objects
-            .prefetch_related('transfers')
-            .order_by('-at'))
+    transfers_pre = Prefetch(
+        'transfers',
+        queryset=(
+            Transfer.objects
+            .select_related('from_acc', 'to_acc')
+        ),
+    )
+
+    transfergroups = (
+        TransferGroup.objects
+        .select_related('valid_by')
+        .prefetch_related(transfers_pre)
+        .order_by('-at')
+    )
     return render(request, 'kfet/transfers.html', {
         'transfergroups': transfergroups,
     })
 
+
 @teamkfet_required
 def transfers_create(request):
     transfer_formset = TransferFormSet(queryset=Transfer.objects.none())