@Override public String[] determineColumnConstraints(ResultProducer rp) throws Exception {
  return null;
}

@ Override public String [ ] determineColumnConstraints ( ResultProducer rp ) throws Exception { return null ; }
determines if there are any constraints ( imposed by the destination ) on the result columns to be produced by resultproducers . null should be returned if there are no constraints , otherwise a list of column names should be returned as an array of strings .
