Change derived storage to be based on image

Fixes #971

data/model/image.py

@@ -8,8 +8,8 @@ from datetime import datetime
 from data.model import (DataModelException, db_transaction, _basequery, storage,
                         InvalidImageException, config)
 from data.database import (Image, Repository, ImageStoragePlacement, Namespace, ImageStorage,
-                           ImageStorageLocation, RepositoryPermission, db_for_update,
-                           db_random_func)
+                           ImageStorageLocation, RepositoryPermission, DerivedStorageForImage,
+                           ImageStorageTransformation, db_random_func, db_for_update)
 
 
 logger = logging.getLogger(__name__)
@@ -542,3 +542,48 @@ def set_secscan_status(image, indexed, version):
    .update(security_indexed=indexed, security_indexed_engine=version)
    .where(Image.id << ids_to_update)
    .execute())
+
+
+def find_or_create_derived_storage(source_image, transformation_name, preferred_location):
+  existing = find_derived_storage_for_image(source_image, transformation_name)
+  if existing is not None:
+    return existing
+
+  logger.debug('Creating storage dervied from source image: %s', source_image.id)
+  trans = ImageStorageTransformation.get(name=transformation_name)
+  new_storage = storage.create_v1_storage(preferred_location)
+  DerivedStorageForImage.create(source_image=source_image, derivative=new_storage,
+                                transformation=trans)
+  return new_storage
+
+
+def find_derived_storage_for_image(source_image, transformation_name):
+  try:
+    found = (ImageStorage
+             .select(ImageStorage, DerivedStorageForImage)
+             .join(DerivedStorageForImage)
+             .join(ImageStorageTransformation)
+             .where(DerivedStorageForImage.source_image == source_image,
+                    ImageStorageTransformation.name == transformation_name)
+             .get())
+
+    found.locations = {placement.location.name for placement in found.imagestorageplacement_set}
+    return found
+  except ImageStorage.DoesNotExist:
+    return None
+
+
+def delete_derived_storage_by_uuid(storage_uuid):
+  try:
+    image_storage = storage.get_storage_by_uuid(storage_uuid)
+  except InvalidImageException:
+    return
+
+  try:
+    DerivedStorageForImage.get(derivative=image_storage)
+  except DerivedStorageForImage.DoesNotExist:
+    return
+
+  image_storage.delete_instance(recursive=True)
+
+