试试这个，很相似：

A = LOAD 'test.csv' USING PigStorage('|') as (a1,a2,a3);
    unique  =
        FOREACH (GROUP A BY a3) {
            b = A.(a1,a2);
            s = DISTINCT b;
            GENERATE FLATTEN(s), group AS a4;
        };

方法1：使用distinct
裁判：http://pig.apache.org/docs/r0.12.0/basic.html#distinct
distinct运算符应该有帮助

test = LOAD 'test.csv' USING PigStorage('|');
distinct_recs = DISTINCT test;
DUMP distinct_recs;

方法2：按所有字段分组

test = LOAD 'test.csv' USING PigStorage('|');
grp_all_fields = GROUP test BY ($0,$1,$2);
uniq_recs = FOREACH grp_all_fields GENERATE FLATTEN(group);
DUMP uniq_recs;

这两种方法都给出了共享输入的预期输出。