可能只需使用内置函数就可以得到结果，但简单的自定义项也可以做到这一点：

public class SlidingTuple extends EvalFunc<DataBag> {

    private static final BagFactory bagFactory = BagFactory.getInstance();
    private static final TupleFactory tupleFactory = TupleFactory.getInstance();

    @Override
    public DataBag exec(Tuple input) throws IOException {
        try {
            DataBag inputBag = (DataBag) input.get(0);
            DataBag result = null;
            if (inputBag != null) {
                result = bagFactory.newDefaultBag();
                Iterator<Tuple> it = inputBag.iterator();
                Tuple previous = it.next();
                while (it.hasNext()) {
                    Tuple current = it.next();
                    Tuple tuple = tupleFactory.newTuple(2);
                    tuple.set(0, previous.get(0));
                    tuple.set(1, current.get(0));
                    result.add(tuple);
                    previous = current;
                }
            }
            return result;
        }
        catch (Exception e) {
            throw new RuntimeException("SlidingTuple error", e);
        }
    }
}

然后：

A = LOAD '/user/hive/warehouse/twitter_raw/$date' USING PigStorage('\t') 
      AS (id:chararray,  mess:chararray);

B = foreach A generate TOKENIZE(mess, ' ') as words;

然后使用自定义自定义自定义项：

C = foreach B generate com.example.SlidingTuple(words);