Have get_parent_images not join on placements

The only case that needs the placements is in verbs, for which we use a new method

data/model/image.py

@@ -34,26 +34,41 @@ def get_repository_image_and_deriving(docker_image_id, storage_uuid):
                               (Image.id == image_found.id))
 
 
+def get_parent_images_with_placements(namespace_name, repository_name, image_obj):
+  """ Returns a list of parent Image objects starting with the most recent parent
+      and ending with the base layer. The images in this query will include the storage and
+      placements.
+  """
+  return _get_parent_images(namespace_name, repository_name, image_obj, include_placements=True)
+
+
 def get_parent_images(namespace_name, repository_name, image_obj):
   """ Returns a list of parent Image objects starting with the most recent parent
-      and ending with the base layer.
+      and ending with the base layer. The images in this query will include the storage but
+      not the placements.
   """
+  return _get_parent_images(namespace_name, repository_name, image_obj, include_placements=False)
+
+
+def _get_parent_images(namespace_name, repository_name, image_obj, include_placements=False):
   parents = image_obj.ancestors
 
   # Ancestors are in the format /<root>/<intermediate>/.../<parent>/, with each path section
   # containing the database Id of the image row.
   parent_db_ids = parents.strip('/').split('/')
-
   if parent_db_ids == ['']:
     return []
 
   def filter_to_parents(query):
     return query.where(Image.id << parent_db_ids)
 
-  parents = get_repository_images_base(namespace_name, repository_name, filter_to_parents)
+  if include_placements:
+    parents = get_repository_images_base(namespace_name, repository_name, filter_to_parents)
+  else:
+    parents = _get_repository_images_and_storages(namespace_name, repository_name,
+                                                  filter_to_parents)
 
   id_to_image = {unicode(image.id): image for image in parents}
-
   return [id_to_image[parent_id] for parent_id in reversed(parent_db_ids)]
 
 
@@ -79,6 +94,19 @@ def get_repo_image_extended(namespace_name, repository_name, docker_image_id):
   return images[0]
 
 
+def _get_repository_images_and_storages(namespace_name, repository_name, query_modifier):
+  query = (Image
+           .select(Image, ImageStorage)
+           .join(ImageStorage)
+           .switch(Image)
+           .join(Repository)
+           .join(Namespace, on=(Repository.namespace_user == Namespace.id))
+           .where(Repository.name == repository_name, Namespace.username == namespace_name))
+
+  query = query_modifier(query)
+  return query
+
+
 def _get_repository_images(namespace_name, repository_name, query_modifier):
   query = (Image
            .select()

endpoints/verbs.py

@@ -37,7 +37,8 @@ def _open_stream(formatter, namespace, repository, tag, synthetic_image_id, imag
   # For performance reasons, we load the full image list here, cache it, then disconnect from
   # the database.
   with database.UseThenDisconnect(app.config):
-    image_list = list(model.image.get_parent_images(namespace, repository, repo_image))
+    image_list = list(model.image.get_parent_images_with_placements(namespace, repository,
+                                                                    repo_image))
     image_list.insert(0, repo_image)
 
   def get_image_json(image):