未经测试，但我采用的一般方法是：获取一个包含id和一包值的变量，将其展平，使您只得到id和单个值的行，获取不同的行，然后按id分组。这将为每个id提供一包值，如果您想输出，可以将其转换为字符串。

A = LOAD 'input' USING TextLoader() as line:chararray; 
B = FOREACH A GENERATE STRSPLIT(line,',',2) as (id:chararray,values:chararray)
C = FOREACH B GENERATE id, FLATTEN(TOBAG(STRSPLIT(values,','))) as value:chararray;
D = DISTINCT C; -- I'm assuming you actually want distinct values, wasn't clear.
E = GROUP D by id;
F = FOREACH E GENERATE group as id, BagToString(D.value) as valueString:chararray;