hadoop - 在Pig中处理数据结构

Question

之前我问过Hive或Pig中的manipulating a data structure。我能够在SQL中得到答案，然后从那里找出Hive的答案。我仍在寻找Pig的解决方案。

我想更改myTable:


进入myTable2:


我试过了:

myTable2 = FOREACH myTable GENERATE item, year, 
'jan' AS month, jan AS value, 
'feb' AS month, feb AS value,  
'mar' AS month, mar AS value;

在Hive中工作大致相同，但Pig给我的好处是:

ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1108:
<line 2, column 35> Duplicate schema alias: month

Answer 1

我想通了，尽管我希望看到一个更简洁的版本:

JAN = FOREACH myTable GENERATE item, year, 'jan' AS month, jan AS value;
FEB = FOREACH myTable GENERATE item, year, 'feb' AS month, feb AS value;
MAR = FOREACH myTable GENERATE item, year, 'mar' AS month, mar AS value;
myTable2 = union JAN, FEB, MAR;