PIG 集团 by avoid Bag

Question

这是一个基本的 PIG 问题。我的数据是这样的

10  | Dog
15 | Cow
20 | Dog
15 | Elephant
15 | Dog
25 | Elephant

我想找出每只动物的平均体重并得到如下输出：

Dog | 12.5
Elephant | 20
Cow | 15

我可以使用 GROUP by 并得到结果，但结果是一个包，像这样：

 {(Dog), (Dog) } | 12.5
 {(Elephant), (Elephant)} | 20
 {(Cow)} | 15

我怎样才能只提取单个动物？

我是这样使用GROUP的。

--animal_weight is derived through other means
animal_by = GROUP animal_weight by (animal);
results = FOREACH animal_by GENERATE animal_weight.animal as animal_name, AVG(animal_weight.weight) as kg;
STORE results INTO '$output_4' USING PigStorage('|');

Answer 1

使用group而不是animal_weight.animal。请注意，根据您的示例数据，狗的平均体重应为 (10+20+15)/3 = 15 公斤

results = FOREACH animal_by GENERATE group as animal_name, AVG(animal_weight.weight) as kg;

输出

PIG 集团 by avoid Bag

PIG Group by avoid Bag

apache-pig