测试数据文件foreach_bag.log，内容如下：
{('b', 55), ('sally', 52), ('john', 25)}
{('c', 355), ('msally', 352), ('mjohn', 325)}
foreach_bag.pig代码如下：
A = LOAD 'foreach_bag.log' as (b:bag{t:(x:chararray, y:int)});
describe A;
B = foreach A generate COUNT(b);
--B = foreach A generate b;
dump B;
执行命令：pig -x local foreach_bag.pig
结果如下：
(3)
(3)