replacing values in pig latin

问题

I have a dataset in form:

id1, id2, id3

Either of id1,id2 or id3 (or all three.. or any two) can be missing in a record.

Now if id1 is missing I want to replace it with 1

 id2 by 3 
 id3 by 7

How do I do this. Thanks

回答1:

Use the bincond operator to test if the value is null and then replace it with the desired value. From Programming Pig, Chapter 5:

2 == 2 ? 1 : 4 --returns 1 
2 == 3 ? 1 : 4 --returns 4 
null == 2 ? 1 : 4 -- returns null
2 == 2 ? 1 : 'fred' -- type error, both values must be of the same type

In your example,

id2 IS NULL ? 3 : id2

来源：https://stackoverflow.com/questions/13386609/replacing-values-in-pig-latin