REST: Fix duplicate project queries

Eliminates duplicate project queries caused by calling
get_absolute_url() in the embedded serializers. Following foreign keys
with 'series__project' will cache the project of the series as well as
the series itself.

Signed-off-by: Mete Polat <metepolat2000@gmail.com>
Signed-off-by: Stephen Finucane <stephen@that.guru>
Closes: #335
(backported from commit ec00daa
  dropped all the tests, they clash horribly)
Signed-off-by: Daniel Axtens <dja@axtens.net>

Author: metp

patchwork/api/cover.py

@@ -103,7 +103,8 @@ class CoverLetterList(ListAPIView):
     ordering = 'id'
 
     def get_queryset(self):
-        return CoverLetter.objects.all().prefetch_related('series')\
+        return CoverLetter.objects.all().prefetch_related('series',
+                                                          'series__project')\
             .select_related('project', 'submitter')\
             .defer('content', 'headers')
 

patchwork/api/event.py

@@ -96,7 +96,7 @@ class EventList(ListAPIView):
 
     def get_queryset(self):
         return Event.objects.all()\
-            .prefetch_related('project', 'patch', 'series', 'cover',
-                              'previous_state', 'current_state',
+            .prefetch_related('project', 'patch__project', 'series__project',
+                              'cover', 'previous_state', 'current_state',
                               'previous_delegate', 'current_delegate',
                               'created_check')

patchwork/api/patch.py

@@ -187,8 +187,9 @@ class PatchList(ListAPIView):
 
     def get_queryset(self):
         return Patch.objects.all()\
-            .prefetch_related('series', 'check_set')\
-            .select_related('project', 'state', 'submitter', 'delegate')\
+            .prefetch_related('series', 'check_set', 'series__project')\
+            .select_related('project', 'state', 'submitter', 'delegate',
+                            )\
             .defer('content', 'diff', 'headers')
 
 

patchwork/api/series.py

@@ -69,8 +69,9 @@ class SeriesMixin(object):
     serializer_class = SeriesSerializer
 
     def get_queryset(self):
-        return Series.objects.all().prefetch_related('patches',)\
-            .select_related('submitter', 'cover_letter', 'project')
+        return Series.objects.all()\
+            .prefetch_related('patches__project',)\
+            .select_related('submitter', 'cover_letter__project', 'project')
 
 
 class SeriesList(SeriesMixin, ListAPIView):