Basic labels support

Adds basic labels support to the registry code (V2), and the API. Note that this does not yet add any UI related support.

data/model/tag.py

@@ -5,7 +5,8 @@ from uuid import uuid4
 from data.model import (image, db_transaction, DataModelException, _basequery,
                         InvalidManifestException)
 from data.database import (RepositoryTag, Repository, Image, ImageStorage, Namespace, TagManifest,
-                           RepositoryNotification, get_epoch_timestamp, db_for_update)
+                           RepositoryNotification, Label, TagManifestLabel, get_epoch_timestamp,
+                           db_for_update)
 
 
 logger = logging.getLogger(__name__)
@@ -150,6 +151,22 @@ def garbage_collect_tags(repo):
 
       num_deleted_manifests = 0
       if len(manifests_to_delete) > 0:
+        # Find the set of IDs for all the labels to delete.
+        labels = list(TagManifestLabel
+                      .select(TagManifestLabel.id)
+                      .where(TagManifestLabel.annotated << manifests_to_delete))
+
+        if len(labels) > 0:
+          # Delete the mapping entries.
+          (TagManifestLabel
+           .delete()
+           .where(TagManifestLabel.annotated << manifests_to_delete)
+           .execute())
+
+          # Delete the labels themselves.
+          Label.delete().where(Label.id << [label.id for label in labels]).execute()
+
+        # Delete the tag manifests themselves.
         num_deleted_manifests = (TagManifest
                                  .delete()
                                  .where(TagManifest.id << manifests_to_delete)
@@ -234,15 +251,22 @@ def revert_tag(repo_obj, tag_name, docker_image_id):
 
 def store_tag_manifest(namespace, repo_name, tag_name, docker_image_id, manifest_digest,
                        manifest_data):
+  """ Stores a tag manifest for a specific tag name in the database. Returns the TagManifest
+      object, as well as a boolean indicating whether the TagManifest was created or updated.
+  """
   with db_transaction():
     tag = create_or_update_tag(namespace, repo_name, tag_name, docker_image_id)
 
     try:
       manifest = TagManifest.get(digest=manifest_digest)
+      if manifest.tag == tag:
+        return manifest, False
+
       manifest.tag = tag
       manifest.save()
+      return manifest, True
     except TagManifest.DoesNotExist:
-      return TagManifest.create(tag=tag, digest=manifest_digest, json_data=manifest_data)
+      return TagManifest.create(tag=tag, digest=manifest_digest, json_data=manifest_data), True
 
 
 def get_active_tag(namespace, repo_name, tag_name):
@@ -282,7 +306,7 @@ def load_manifest_by_digest(namespace, repo_name, digest):
 
 def _load_repo_manifests(namespace, repo_name):
     return _tag_alive(TagManifest
-                      .select(TagManifest, RepositoryTag)
+                      .select(TagManifest, RepositoryTag, Repository)
                       .join(RepositoryTag)
                       .join(Repository)
                       .join(Namespace, on=(Namespace.id == Repository.namespace_user))