使用Hive UDF计算权重因子

Question

I'm newbie to Hive, I would an help to write an UDF function for weighting factor calculation.

The calculation seems simple.

I have one table with some values KEY,VALUE grouped by GROUP_ID . For each row of one group I want calculate the weighting factor, a float beetween 0 and 1 that's the weight of that element of the group . The sum of weighting factors into the group must be 1.

In this example the value is the distance, then the weight is inversely proportional to the distance.

GROUP_ID | KEY     | VALUE(DISTANCE)
====================================
1          10        4
1          11        3
1          12        2
2          13        1
2          14        5
3          ..        ..
...

Math function: 1/(Xi * sum(1/Xk)) from k=1 to N)

GROUP_ID | KEY |   VALUE    | WEIGHTING_FACTOR
=======================================================
1          10      4        1/(4*(1/4+1/3+1/2)) = 0.23
1          11      3        1/(3*(1/4+1/3+1/2)) = 0.31
1          12      2        1/(2*(1/4+1/3+1/2)) = 0.46
2          13      1        1/(1*(1/1+1/5)) = 0.83
2          14      5        1/(5*(1/1+1+5)) = 0.17
3          ..      ..
...

Have you a suggestion for using UDF, UDAF or UDTF function?

Maybe I must use a "Transform"? https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Transform

Answer 1

Solved using Windowing and Analytics Functions

http://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.0.0.2/ds_Hive/language_manual/ptf-window.html

Source: https://stackoverflow.com/a/18919834/2568351