在 Pig 中使用多个条件过滤列

Posted 2023-04-18

【中文标题】在 Pig 中使用多个条件过滤列

【英文标题】：Filter columns using multiple conditions in Pig

【发布时间】：2016-11-14 21:52:41

【问题描述】：

我需要编写一个 pig 脚本，在其中找到几列的平均值，并只获取所有列值都大于计算平均值的那些行。我的脚本是：

i2 = GROUP i1 all;
i3 = FOREACH i2 GENERATE AVG(i1.user_followers_count) AS avg_user_followers_count, AVG(i1.avl_user_follower_following_ratio) AS avg_avl_user_follower_following_ratio, AVG(i1.user_total_liked) AS avg_user_total_liked, AVG(i1.user_total_posts) AS avg_user_total_posts, AVG(i1.user_total_public_lists) AS avg_user_total_public_lists, AVG(i1.avl_user_total_retweets) AS avg_avl_user_total_retweets, AVG(i1.avl_user_total_likes) AS avl_user_total_likes, AVG(i1.avl_user_total_replies) AS avg_avl_user_total_replies, AVG(i1.avl_user_engagements) AS avl_avl_user_engagements, AVG(i1.user_reply_to_reply_count) AS avg_user_reply_to_reply_count;

top_inf = FILTER i1 BY (i1.user_followers_count > i3.avg_user_followers_count, i1.avl_user_total_retweets > i3. avg_avl_user_total_retweets, i1.avl_user_total_likes > i3.avg_avl_user_total_retweets);

但这会引发错误：

ERROR 1200: <file user.pig, line 70, column 103>  mismatched input '>' expecting RIGHT_PAREN

在多个条件下过滤行的正确方法是什么？

【参考方案1】：

使用 AND 分隔条件

top_inf = FILTER i1 BY (i1.user_followers_count > i3.avg_user_followers_count) 
                   AND (i1.avl_user_total_retweets > i3.avg_avl_user_total_retweets) 
                   AND (i1.avl_user_total_likes > i3.avg_avl_user_total_retweets);

【讨论】：

我们需要在每个 AND 条件周围使用大括号吗？