Apache Pig AVG 函数

Question

我正在尝试做一个简单的 Pig 查询，我需要在其中找到 ID 为 178 的电影的平均评分。我已经尝试了下面的多个版本并且过滤器工作但 AVG 不工作功能。谁能建议？谢谢

a = load '/user/pig/u.data' AS (userid:int, movieid:int, rating:double, timestamp:chararray);  
b = FOREACH a GENERATE AVG(rating) as rate, movieid;
c = group b by rate;
d= filter a by movieid==178;
dump d;

Answer 1

你应该按 movieid 分组

b = FILTER a BY (movieid == 178);
c = GROUP b BY movied;
d = FOREACH c GENERATE group AS movieid,AVG(a.rating) as rate;