private Set<String> primaryKeys(PreparedStatement stmt,String owner,String tbl) throws SQLException {
  Set<String> pkCols=new HashSet<>();
  stmt.setString(1,owner);
  stmt.setString(2,tbl);
  try (ResultSet pkRs=stmt.executeQuery()){
    while (pkRs.next())     pkCols.add(pkRs.getString(1));
  }
   return pkCols;
}

private Set < String > primaryKeys ( PreparedStatement stmt , String owner , String tbl ) throws SQLException { Set < String > pkCols = new HashSet < > ( ) ; stmt . setString ( 1 , owner ) ; stmt . setString ( 2 , tbl ) ; try ( ResultSet pkRs = stmt . executeQuery ( ) ) { while ( pkRs . next ( ) ) pkCols . add ( pkRs . getString ( 1 ) ) ; } return pkCols ; }
retrieve primary key columns .
