Apache Pig Rank函数的用法 [英] Usage of Apache Pig rank function

问题描述

Am使用Pig 0.11.0等级函数，并为数据中的每个id生成等级. 我需要以特定方式对数据进行排名.我希望重置等级并为每个新ID从1开始.

Am using Pig 0.11.0 rank function and generating ranks for every id in my data. I need ranking of my data in a particular way. I want the rank to reset and start from 1 for every new ID.

是否可以直接将rank函数用于同一个? 任何提示将不胜感激.

Is it possible to use the rank function directly for the same? Any tips would be appreciated.

数据:

id,rating
X001, 9
X001, 9
X001, 8
X002, 9
X002, 7
X002, 6
X002, 5
X003, 8
X004, 8
X004, 7
X004, 7
X004, 4

在使用排名函数时，例如: op =按ID，得分对数据进行排名；

On using rank function like: op = rank data by id,score;

我得到这个输出

rank,id,rating
1, X001, 9
1, X001, 9
2, X001, 8
3, X002, 9
4, X002, 7
5, X002, 6
6, X002, 5
7, X003, 8
8, X004, 8
9, X004, 7
9, X004, 7
10, X004, 4

所需的O/P:

rank,id,rating
1, X001, 9
1, X001, 9
2, X001, 8
1, X002, 9
2, X002, 7
3, X002, 6
4, X002, 5
1, X003, 8
1, X004, 8
2, X004, 7
2, X004, 7
3, X004, 4

推荐答案

您可以按ID对数据进行分组，然后使用UDF

You can group your data by id then use the UDF Enumerate (DataFu) to append an index to each tuple of the bags.

register datafu-1.1.0.jar;
define Enumerate datafu.pig.bags.Enumerate('1');

data = load 'data' using PigStorage(',') as (id:chararray, rating:int);
data = group data by id;
data = foreach data {
  sorted = order data by rating DESC;
  generate group, sorted;
}
data = foreach data generate FLATTEN(Enumerate(sorted));
data = foreach data generate $2, $0, $1;
dump data;

可以从Maven Central存储库下载

DataFu jar文件: http ://search.maven.org/#search | ga | 1 | g％3A％22com.linkedin.datafu％22

DataFu jar file can be downloaded from Maven Central repository: http://search.maven.org/#search|ga|1|g%3A%22com.linkedin.datafu%22

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