Apache Pig rank函数的使用 [英] Usage of Apache Pig rank function
问题描述
我使用 Pig 0.11.0 rank 函数并为我的数据中的每个 id 生成排名.我需要以特定方式对我的数据进行排名.我希望每个新 ID 的排名都重置并从 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.
是否可以直接使用 rank 函数?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
使用秩函数,如:op = 按 id、score 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
期望的 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 Enumerate (DataFu) 为包的每个元组附加一个索引.
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;
DataFu jar 文件可以从 Maven 中央存储库下载: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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