[PATCH] xmlrpc: Don't load all Patches into memory

[Stephen Finucane]

The way that reverse indexing of patches was implemented is broken.
At present, it will retrieve all patches in memory and return the
length from that data, then the slicing operation will then happen
without querying the DB and slice the results cached from the len()
evaluation. This is memory intensive, particularly for larger
instances.

Take advantage of Django's lazy loading to avoid this.

Signed-off-by: Stephen Finucane <stephen.finucane at intel.com>
Suggested-by: Damien Lespiau <damien.lespiau at intel.com>
---
 patchwork/views/xmlrpc.py |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/patchwork/views/xmlrpc.py b/patchwork/views/xmlrpc.py
index 638b3b1..8f759aa 100644
--- a/patchwork/views/xmlrpc.py
+++ b/patchwork/views/xmlrpc.py
@@ -406,8 +406,8 @@ def project_list(search_str=None, max_count=0):
         if max_count > 0:
             return list(map(project_to_dict, projects[:max_count]))
         elif max_count < 0:
-            return list(map(project_to_dict,
-                            projects[len(projects) + max_count:]))
+            query = projects.reverse()[:-max_count]
+            return list(map(project_to_dict, reversed(query)))
         else:
             return list(map(project_to_dict, projects))
     except Project.DoesNotExist:
@@ -461,7 +461,8 @@ def person_list(search_str=None, max_count=0):
         if max_count > 0:
             return list(map(person_to_dict, people[:max_count]))
         elif max_count < 0:
-            return list(map(person_to_dict, people[len(people) + max_count:]))
+            query = people.reverse()[:-max_count]
+            return list(map(person_to_dict, reversed(query)))
         else:
             return list(map(person_to_dict, people))
     except Person.DoesNotExist:
@@ -606,8 +607,8 @@ def patch_list(filt=None):
         if max_count > 0:
             return list(map(patch_to_dict, patches[:max_count]))
         elif max_count < 0:
-            return list(map(patch_to_dict,
-                            patches[len(patches) + max_count:]))
+            query = patches.reverse()[:-max_count]
+            return list(map(patch_to_dict, reversed(query)))
         else:
             return list(map(patch_to_dict, patches))
     except Patch.DoesNotExist:
@@ -802,7 +803,8 @@ def state_list(search_str=None, max_count=0):
         if max_count > 0:
             return list(map(state_to_dict, states[:max_count]))
         elif max_count < 0:
-            return list(map(state_to_dict, states[len(states) + max_count:]))
+            query = states.reverse()[:-max_count]
+            return list(map(state_to_dict, reversed(query)))
         else:
             return list(map(state_to_dict, states))
     except State.DoesNotExist:
-- 
1.7.4.1