DSpace: Determine Size of a bottom-level Sub-community

gistfile1.sql

SELECT size_bytes 
FROM bitstream , item2bundle, bundle2bitstream
WHERE item2bundle.bundle_id = bundle2bitstream.bundle_id 
  AND bundle2bitstream.bitstream_id = bitstream.bitstream_id
  AND item2bundle.item_id = ANY(
    SELECT item_id 
    FROM item 
    WHERE owning_collection = ANY(
      SELECT collection_id 
      FROM community2collection 
      WHERE community_id = 53
    )
  )