Apache pig 如何找到pig中排名前两位的收视率？

我的数据如下所示：

USA,10  
UK,8  
INDIA,8  
PAKISTAN,5  
U.A.E,3  
GERMANY,3  
SWEDEN,2

我如何获得前两个评级最高的国家？根据上述示例数据，我希望：

UK,8  
INDIA,8 

你能试试这个吗

更新：
如果pig版本中没有

RANK

操作符，那么使用本机pig很难解决此问题。一个选项可以是下载

pig-0.11.1.jar

，并将其设置在类路径中，然后尝试以下方法

input.txt

USA,10
UK,8
INDIA,8
PAKISTAN,5
U.A.E,3
GERMANY,3
SWEDEN,2

PigScript:

DEFINE MyOver org.apache.pig.piggybank.evaluation.Over('myrank:int');
DEFINE MyStitch org.apache.pig.piggybank.evaluation.Stitch;

A = LOAD 'input.txt' USING PigStorage(',') AS (country:chararray,rating:int);
B = GROUP A ALL;
C = FOREACH B  {
                 mysort = ORDER A BY rating DESC;
                 GENERATE FLATTEN(MyStitch(mysort,MyOver(mysort,'dense_rank',0,1,1)));
                }
D = FILTER C BY stitched::myrank==2;
E = FOREACH D GENERATE stitched::country AS country,stitched::rating AS rating;
DUMP E;

(UK,8)
(INDIA,8)

(UK,8)
(INDIA,8)

输出：

DEFINE MyOver org.apache.pig.piggybank.evaluation.Over('myrank:int');
DEFINE MyStitch org.apache.pig.piggybank.evaluation.Stitch;

A = LOAD 'input.txt' USING PigStorage(',') AS (country:chararray,rating:int);
B = GROUP A ALL;
C = FOREACH B  {
                 mysort = ORDER A BY rating DESC;
                 GENERATE FLATTEN(MyStitch(mysort,MyOver(mysort,'dense_rank',0,1,1)));
                }
D = FILTER C BY stitched::myrank==2;
E = FOREACH D GENERATE stitched::country AS country,stitched::rating AS rating;
DUMP E;

(UK,8)
(INDIA,8)

(UK,8)
(INDIA,8)

清管器版本>11支持等级操作员

A = LOAD 'input.txt' USING PigStorage(',') AS (country:chararray,rating:int);
B = RANK A BY rating DESC;
C = FILTER B BY rank_A==2;
D = FOREACH C GENERATE country,rating;
DUMP D;

输出：

DEFINE MyOver org.apache.pig.piggybank.evaluation.Over('myrank:int');
DEFINE MyStitch org.apache.pig.piggybank.evaluation.Stitch;

A = LOAD 'input.txt' USING PigStorage(',') AS (country:chararray,rating:int);
B = GROUP A ALL;
C = FOREACH B  {
                 mysort = ORDER A BY rating DESC;
                 GENERATE FLATTEN(MyStitch(mysort,MyOver(mysort,'dense_rank',0,1,1)));
                }
D = FILTER C BY stitched::myrank==2;
E = FOREACH D GENERATE stitched::country AS country,stitched::rating AS rating;
DUMP E;

(UK,8)
(INDIA,8)

(UK,8)
(INDIA,8)

---

我的hadoop pig版本是0.8.0，我不能使用RANK。更新了另一种方法，我希望这对你有用。