Pig WordCount案例学习(flatten,TOKENIZE)

WordCount实现
-- ① 加载数据
a= load '/input/data' as (line:chararray);
-- ② 将字符串分割成单词
b= foreach a generate flatten(TOKENIZE(line)) as word;
-- ③ 对单词进行分组
c= group words by word;
-- ④ 统计每组中单词数量
d= foreach c generate group,COUNT(b);    
-- ⑤ 打印结果
dump cntd;

foreach a generate group ：对c中所有key进行分组
a = (a,{})(b,{})(b,{}):foreach a generate group =>得到(a,b,c)
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line = (lin lin lin)
TOKENIZE：foreach a generate TOKENIZE(line,'') =>({(lin),(lin),(lin)})

flatten：会把集合的内容打开然后组合一个元组； ({(lin),(lin),(lin)}) =>(lin)(lin)(lin)