Optimize get_tag_image query

No caller uses the image placements or locations, so no need to load them.

data/model/tag.py

@@ -162,20 +162,40 @@ def garbage_collect_tags(repo):
 
       logger.debug('Removed %s tags with %s manifests', num_deleted_tags, num_deleted_manifests)
 
-def get_tag_image(namespace_name, repository_name, tag_name):
-  def limit_to_tag(query):
-    return _tag_alive(query
-                      .switch(Image)
-                      .join(RepositoryTag)
-                      .where(RepositoryTag.name == tag_name))
 
-  images = image.get_repository_images_base(namespace_name, repository_name, limit_to_tag)
+def _get_repo_tag_image(tag_name, include_storage, modifier):
+  query = Image.select().join(RepositoryTag)
+
+  if include_storage:
+    query = (Image.select(Image, ImageStorage)
+                  .join(ImageStorage)
+                  .switch(Image)
+                  .join(RepositoryTag))
+
+  images = _tag_alive(modifier(query.where(RepositoryTag.name == tag_name)))
   if not images:
     raise DataModelException('Unable to find image for tag.')
   else:
     return images[0]
 
 
+def get_repo_tag_image(repo, tag_name, include_storage=False):
+  def modifier(query):
+    return query.where(RepositoryTag.repository == repo)
+
+  return _get_repo_tag_image(tag_name, include_storage, modifier)
+
+
+def get_tag_image(namespace_name, repository_name, tag_name, include_storage=False):
+  def modifier(query):
+    return (query.switch(RepositoryTag)
+                 .join(Repository)
+                 .join(Namespace)
+                 .where(Namespace.username == namespace_name, Repository.name == repository_name))
+
+  return _get_repo_tag_image(tag_name, include_storage, modifier)
+
+
 def list_repository_tag_history(repo_obj, page=1, size=100, specific_tag=None):
   query = (RepositoryTag
            .select(RepositoryTag, Image)