Apache Pig Distinct和Count

Question

我想弄清楚以下问题。

有多少女性用户提供了至少一个4的评分。我认为我的加入和过滤器是正确的但是我无法弄清楚明显的计数部分已经尝试了下面的多个版本。

a = load '/user/pig/movie' AS (userid:int, movieid:int, rating:int, timestamp:chararray);
b = load '/user/pig/reviewer' using PigStorage('|') AS (userid:int, age:int, gender:chararray, occupation:chararray, zip:chararray);
a1 = filter a by rating == 4;
b1 = filter b by gender == 'F';
c = join a1 by userid, b1 by userid;
d = FOREACH c GENERATE COUNT(DISTINCT(userid));
dump d;

Answer 1

你必须在COUNT之前进行GROUP。回复：COUNT需要一个前面的GROUP ALL语句用于全局计数，一个GROUP BY语句用于组计数。

d = GROUP c BY userid;
e = FOREACH d GENERATE COUNT(DISTINCT(b1.userid));
dump e;