PIG 中的标量投影无效

Question

我在 PIG 中有数据，列名为

关键字、campaign_id、日期、时间、display_site、was_clicked、cpc、国家、展示位置

我想做的是找到点击率高的关键字。

所以，我试图理解为什么下面的代码给了我 Invalid Scalar projection 错误

  grouped = GROUP data BY keyword;
  by_keyword = FOREACH grouped 
{
  clicked = FILTER data BY was_clicked == 1;
  total = COUNT(data.keyword);
  GENERATE group, ((double)COUNT(clicked) / total) AS ctr;
}

我得到的错误：

37,632 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1200: Pig script failed to parse: 
<line 59, column 33> Invalid scalar projection: clicked : A column needs to be projected from a relation for it to be used as a scalar
Details at logfile: /home/cloudera/pig_1486224821223.log

任何帮助将不胜感激。

编辑：

data = LOAD '/user/cloudera/pig_demo/ad_data.txt' AS (keyword:chararray,campaign_id:chararray,
      date:chararray, time:chararray,display_site:chararray, was_clicked:int, 
      cpc:int, country:chararray, placement:chararray);

记录样本：

tablet  C6  5/1/2013    3:47:10 movienet.example.com    0   102 USA TOP

Answer 1

猪 0.15 版。

输入文件data.txt:

tablet  C6  5/1/2013    3:47:10 movienet.example.com    0   102 USA TOP
tablet  C6  5/1/2013    3:47:10 movienet.example.com    0   102 USA TOP
tablet  C6  5/1/2013    3:47:10 movienet.example.com    0   102 USA TOP
tablet  C6  5/1/2013    3:47:10 movienet.example.com    1   102 USA TOP

脚本：

data = LOAD '/path/data.txt' AS (keyword:chararray,campaign_id:chararray,
  date:chararray, time:chararray,display_site:chararray, was_clicked:int, 
  cpc:int, country:chararray, placement:chararray);
grouped = GROUP data BY keyword;
by_keyword = FOREACH grouped 
{
  clicked = FILTER data BY was_clicked == 1;
  total = COUNT(data.keyword);
  GENERATE group, ((double)COUNT(clicked) / total) AS ctr;
}
dump by_keyword

给我正确的结果：

(tablet,0.25)