diff --git a/data/migrations/versions/87c29d0cd05_backfill_aggregate_size_columns.py b/data/migrations/versions/87c29d0cd05_backfill_aggregate_size_columns.py
deleted file mode 100644
index 2b6e4bf2a..000000000
--- a/data/migrations/versions/87c29d0cd05_backfill_aggregate_size_columns.py
+++ /dev/null
@@ -1,22 +0,0 @@
-"""Backfill aggregate size columns
-
-Revision ID: 87c29d0cd05
-Revises: 2b2529fd23ff
-Create Date: 2015-03-16 17:55:30.148557
-
-"""
-
-# revision identifiers, used by Alembic.
-revision = '87c29d0cd05'
-down_revision = '2b2529fd23ff'
-
-from alembic import op
-import sqlalchemy as sa
-from util.backfill_aggregate_sizes import backfill_aggregate_sizes
-
-
-def upgrade(tables):
-  backfill_aggregate_sizes()
-
-def downgrade(tables):
-  pass
\ No newline at end of file
diff --git a/data/model/legacy.py b/data/model/legacy.py
index b84b262eb..bde1b4ad8 100644
--- a/data/model/legacy.py
+++ b/data/model/legacy.py
@@ -1454,8 +1454,13 @@ def set_image_size(docker_image_id, namespace_name, repository_name, image_size,
   ancestors = image.ancestors.split('/')[1:-1]
   if ancestors:
     try:
-      parent_image = Image.get(Image.id == ancestors[-1])
-      total_size = image_size + parent_image.storage.aggregate_size
+      # TODO(jschorr): Switch to this faster route once we have full ancestor aggregate_size
+      # parent_image = Image.get(Image.id == ancestors[-1])
+      # total_size = image_size + parent_image.storage.aggregate_size
+      total_size = (ImageStorage.select(fn.Sum(ImageStorage.image_size))
+                                .join(Image)
+                                .where(Image.id << ancestors)) + image_size
+
       image.storage.aggregate_size = total_size
     except Image.DoesNotExist:
       pass
diff --git a/test/test_imagetree.py b/test/test_imagetree.py
index d72eb6505..e257792c4 100644
--- a/test/test_imagetree.py
+++ b/test/test_imagetree.py
@@ -58,7 +58,7 @@ class TestImageTree(unittest.TestCase):
 
     result = tree.find_longest_path(base_image.id, checker)
     self.assertEquals(4, len(result))
-    self.assertEquals('v2.0', tree.tag_containing_image(result[-1]))
+    self.assertEquals('prod', tree.tag_containing_image(result[-1]))
 
   def test_filtering(self):
     all_images = list(model.get_repository_images(NAMESPACE, COMPLEX_REPO))
@@ -88,7 +88,7 @@ class TestImageTree(unittest.TestCase):
 
     # Only use the first two images. They don't have tags, but the method should
     # still return the tag that contains them.
-    self.assertEquals('v2.0', tree.tag_containing_image(result[0]))
+    self.assertEquals('staging', tree.tag_containing_image(result[0]))
 
 
 if __name__ == '__main__':