问题陈述：查找具有最大信誉的用户的displayname和帖子数。
首先利用关系“user”找到信誉度最大的用户的显示名
然后应用带有关系“post”的join来收集该max用户的所有post。。然后根据id应用分组并进行计数。
下面的代码将帮助您实现目标

User = LOAD 'path' USING PigStorage(',') as (id:int, reputation:int, displayname:chararray, loc:chararray, age:int);
Post = LOAD 'path' USING PigStorage(',') as (id:int, post_type:int, creationdate:chararray,score:int, viewcount:int, ownerus)er_id:int, title:chararray, answercount:chararray);
User_grp = GROUP User BY id;
User_each = FOREACH User_grp 
                 {
                   User_order = ORDER User BY reputation DESC;
                   User_limit = LIMIT User_order 1;
                   User_nested = FOREACH User_limit GENERATE id,displayname;
                   GENERATE flatten(user_nested) as  (user_id,displayname);
                 };
User_join = JOIN User_each by user_id, Post by id; 
User_grouping = GROUP User_join BY user_id;
User_output  = FOREACH User_grouping GENERATE group as user_id, MAX(user_join.displayname) as displayname, COUNT(user_join.post_type) as post_cnts;