diff --git a/tools/uncompressedsize.py b/tools/uncompressedsize.py
index 608446bae..1182f0838 100644
--- a/tools/uncompressedsize.py
+++ b/tools/uncompressedsize.py
@@ -4,7 +4,7 @@ import zlib
 from data import model
 from data.database import ImageStorage
 from app import app, storage as store
-from data.database import db
+from data.database import db, db_random_func
 from util.gzipstream import ZLIB_GZIP_WINDOW
 
 
@@ -17,45 +17,50 @@ CHUNK_SIZE = 5 * 1024 * 1024
 def backfill_sizes_from_data():
   while True:
     # Load the record from the DB.
-    try:
-      record = (ImageStorage
-                .select(ImageStorage.uuid)
-                .where(ImageStorage.uncompressed_size >> None, ImageStorage.uploading == False)
-                .get())
-    except ImageStorage.DoesNotExist:
+    batch_ids = list(ImageStorage
+                     .select(ImageStorage.uuid)
+                     .where(ImageStorage.uncompressed_size >> None,
+                            ImageStorage.uploading == False)
+                     .limit(100)
+                     .order_by(db_random_func()))
+    if len(batch_ids) == 0:
       # We're done!
       return
 
-    uuid = record.uuid
+    for record in batch_ids:
+      uuid = record.uuid
 
-    with_locations = model.get_storage_by_uuid(uuid)
-
-    # Read the layer from backing storage and calculate the uncompressed size.
-    logger.debug('Loading data: %s (%s bytes)', uuid, with_locations.image_size)
-    decompressor = zlib.decompressobj(ZLIB_GZIP_WINDOW)
-
-    uncompressed_size = 0
-    with store.stream_read_file(with_locations.locations, store.image_layer_path(uuid)) as stream:
-      while True:
-        current_data = stream.read(CHUNK_SIZE)
-        if len(current_data) == 0:
-          break
-
-        uncompressed_size += len(decompressor.decompress(current_data))
-
-    # Write the size to the image storage. We do so under a transaction AFTER checking to
-    # make sure the image storage still exists and has not changed.
-    logger.debug('Writing entry: %s. Size: %s', uuid, uncompressed_size)
-    with app.config['DB_TRANSACTION_FACTORY'](db):
-      try:
-        current_record = model.get_storage_by_uuid(uuid)
-      except model.InvalidImageException:
-        logger.warning('Storage with uuid no longer exists: %s', uuid)
+      with_locations = model.get_storage_by_uuid(uuid)
+      if with_locations.uncompressed_size is not None:
+        logger.debug('Somebody else already filled this in for us: %s', uuid)
         continue
 
-      if not current_record.uploading and current_record.uncompressed_size == None:
-        current_record.uncompressed_size = uncompressed_size
-        current_record.save()
+      # Read the layer from backing storage and calculate the uncompressed size.
+      logger.debug('Loading data: %s (%s bytes)', uuid, with_locations.image_size)
+      decompressor = zlib.decompressobj(ZLIB_GZIP_WINDOW)
+
+      uncompressed_size = 0
+      with store.stream_read_file(with_locations.locations, store.image_layer_path(uuid)) as stream:
+        while True:
+          current_data = stream.read(CHUNK_SIZE)
+          if len(current_data) == 0:
+            break
+
+          uncompressed_size += len(decompressor.decompress(current_data))
+
+      # Write the size to the image storage. We do so under a transaction AFTER checking to
+      # make sure the image storage still exists and has not changed.
+      logger.debug('Writing entry: %s. Size: %s', uuid, uncompressed_size)
+      with app.config['DB_TRANSACTION_FACTORY'](db):
+        try:
+          current_record = model.get_storage_by_uuid(uuid)
+        except model.InvalidImageException:
+          logger.warning('Storage with uuid no longer exists: %s', uuid)
+          continue
+
+        if not current_record.uploading and current_record.uncompressed_size == None:
+          current_record.uncompressed_size = uncompressed_size
+          current_record.save()
 
 
 if __name__ == "__main__":