code: private void upgradeDelta(TableEntry10 table, 
                              TableUpgrade upgradeTable,
                              Page10 page,
                              Delta10 delta)
      throws IOException
    {
      try (ReadStream is = openRead(page.segment().address(),
                                    page.segment().length())) {
        is.position(delta.address());
        
        long tail = delta.address() + delta.length();
        
        while (is.position() < tail) {
          upgradeDelta(is, table, upgradeTable, page);
        }
      }
    }
docs: Upgrade a table leaf delta.