code: @Override
  	public void clear() {
  		if (dao == null) {
  			return;
  		}
  		CloseableIterator<T> iterator = closeableIterator();
  		try {
  			while (iterator.hasNext()) {
  				iterator.next();
  				iterator.remove();
  			}
  		} finally {
  			IOUtils.closeQuietly(iterator);
  		}
  	}
docs: Clears the collection and uses the iterator to run through the dao and delete all of the items in the collection
  from the associated database table. This is different from removing all of the elements in the table since this
  iterator is across just one item's foreign objects.