From 60cf2dcbd7a7068d0a7300df5acf9e8e7fad3593 Mon Sep 17 00:00:00 2001
From: Jens Gutermuth <jens@gutermuth-online.de>
Date: Mon, 23 Mar 2015 01:58:12 +0100
Subject: [PATCH 1/5] Fix three N+1 queries in pin loading

Fetch the submitter with a join and get all the images and tags in one
query each. This reduces the total query count for loading 50 pins from
304 to 158.

See issue #85.
---
 pinry/core/api.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pinry/core/api.py b/pinry/core/api.py
index 56a4b21..334c019 100644
--- a/pinry/core/api.py
+++ b/pinry/core/api.py
@@ -135,7 +135,8 @@ class PinResource(ModelResource):
         filtering = {
             'submitter': ALL_WITH_RELATIONS
         }
-        queryset = Pin.objects.all()
+        queryset = Pin.objects.all().select_related('submitter'). \
+            prefetch_related('image', 'tags')
         resource_name = 'pin'
         include_resource_uri = False
         always_return_data = True

From 3bcc6d315258b89e1287626137e081c741eeccb3 Mon Sep 17 00:00:00 2001
From: Jens Gutermuth <jens@gutermuth-online.de>
Date: Mon, 23 Mar 2015 02:22:35 +0100
Subject: [PATCH 2/5] Loanding pins does no N+1 queries anymore

This saves another three queries per pin, bringing to total query count
down to 8.

See issue #85 .
---
 pinry/core/api.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/pinry/core/api.py b/pinry/core/api.py
index 334c019..9590f9b 100644
--- a/pinry/core/api.py
+++ b/pinry/core/api.py
@@ -1,3 +1,4 @@
+from django.core.exceptions import ObjectDoesNotExist
 from tastypie import fields
 from tastypie.authorization import DjangoAuthorization
 from tastypie.constants import ALL, ALL_WITH_RELATIONS
@@ -59,7 +60,10 @@ class UserResource(ModelResource):
 
 def filter_generator_for(size):
     def wrapped_func(bundle, **kwargs):
-        return bundle.obj.get_by_size(size)
+        for thumbnail in bundle.obj._prefetched_objects_cache['thumbnail']:
+            if thumbnail.size == size:
+                return thumbnail
+        raise DoesNotExist()
     return wrapped_func
 
 
@@ -136,7 +140,7 @@ class PinResource(ModelResource):
             'submitter': ALL_WITH_RELATIONS
         }
         queryset = Pin.objects.all().select_related('submitter'). \
-            prefetch_related('image', 'tags')
+            prefetch_related('image__thumbnail_set', 'tags')
         resource_name = 'pin'
         include_resource_uri = False
         always_return_data = True

From e4b876916846befa35e288d1a734bd562702cc48 Mon Sep 17 00:00:00 2001
From: Jens Gutermuth <jens@gutermuth-online.de>
Date: Mon, 23 Mar 2015 02:28:21 +0100
Subject: [PATCH 3/5] DoesNotExist should be ObjectDoesNotExist, oops!

---
 pinry/core/api.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pinry/core/api.py b/pinry/core/api.py
index 9590f9b..ea7d30d 100644
--- a/pinry/core/api.py
+++ b/pinry/core/api.py
@@ -63,7 +63,7 @@ def filter_generator_for(size):
         for thumbnail in bundle.obj._prefetched_objects_cache['thumbnail']:
             if thumbnail.size == size:
                 return thumbnail
-        raise DoesNotExist()
+        raise ObjectDoesNotExist()
     return wrapped_func
 
 

From 9d4791b65ad5bbcd01cd2cc21ec838a86896a7b7 Mon Sep 17 00:00:00 2001
From: Jens Gutermuth <jens@gutermuth-online.de>
Date: Mon, 23 Mar 2015 02:30:54 +0100
Subject: [PATCH 4/5] image can be loaded with a join as well (saves another
 query)

---
 pinry/core/api.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pinry/core/api.py b/pinry/core/api.py
index ea7d30d..6cfa069 100644
--- a/pinry/core/api.py
+++ b/pinry/core/api.py
@@ -139,7 +139,7 @@ class PinResource(ModelResource):
         filtering = {
             'submitter': ALL_WITH_RELATIONS
         }
-        queryset = Pin.objects.all().select_related('submitter'). \
+        queryset = Pin.objects.all().select_related('submitter', 'image'). \
             prefetch_related('image__thumbnail_set', 'tags')
         resource_name = 'pin'
         include_resource_uri = False

From deb04500c5ffd3d8e3e679f92d4d1aed7da4cdb2 Mon Sep 17 00:00:00 2001
From: Jens Gutermuth <jens@gutermuth-online.de>
Date: Mon, 23 Mar 2015 03:30:13 +0100
Subject: [PATCH 5/5] Only use prefetched thumbnails if there are there

The optimization broke image uploading, this fixes it again.
---
 pinry/core/api.py | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/pinry/core/api.py b/pinry/core/api.py
index 6cfa069..958d59c 100644
--- a/pinry/core/api.py
+++ b/pinry/core/api.py
@@ -60,10 +60,13 @@ class UserResource(ModelResource):
 
 def filter_generator_for(size):
     def wrapped_func(bundle, **kwargs):
-        for thumbnail in bundle.obj._prefetched_objects_cache['thumbnail']:
-            if thumbnail.size == size:
-                return thumbnail
-        raise ObjectDoesNotExist()
+        if hasattr(bundle.obj, '_prefetched_objects_cache') and 'thumbnail' in bundle.obj._prefetched_objects_cache:
+            for thumbnail in bundle.obj._prefetched_objects_cache['thumbnail']:
+                if thumbnail.size == size:
+                    return thumbnail
+            raise ObjectDoesNotExist()
+        else:
+            return bundle.obj.get_by_size(size)
     return wrapped_func