diff --git a/swh/storage/cassandra/storage.py b/swh/storage/cassandra/storage.py
--- a/swh/storage/cassandra/storage.py
+++ b/swh/storage/cassandra/storage.py
@@ -442,6 +442,8 @@
                 # This allows this function to run in linear time overall instead of
                 # quadratic.
                 for found_content in found_contents_with_same_hash:
+                    # check if the found_content.hashes() dictionary contains a superset
+                    # of the (key, value) pairs in missing_content
                     if missing_content.items() <= found_content.hashes().items():
                         # Found!
                         break