protected int removeCollection(Collection collection, Connection conn)
        throws SQLException {
	PreparedStatement ps = conn.prepareStatement(
	"DELETE FROM " + GMLHSQLIndex.TABLE_NAME + " WHERE SUBSTRING(DOCUMENT_URI, 1, ?) = ?;"
	); 
	ps.setInt(1, collection.getURI().toString().length());
	ps.setString(2, collection.getURI().toString());
	try {
	  return ps.executeUpdate();
	} finally {
	  if (ps != null)
	  ps.close();
	}
      }