Hive UDF实现分析函数row_number

Oracle的分析函数row_number是十分有用的功能,但是將ETL迁移到Hive中发现没有的功能,我们实现了一个UDF实现了该函数,代码如下:

JAVA代码:

package org.nalang.hive.udf;
import org.apache.hadoop.hive.ql.exec.UDF;
public class RowNumber extends UDF {

 private static int MAX_VALUE = 50;
 private static String comparedColumn[] = new String[MAX_VALUE];
 private static int rowNum = 1;
 public int evaluate(Object... args) {
 String columnValue[] = new String[args.length];
 for (int i = 0; i < args.length; i++)
 columnValue[i] = args[i].toString();
 if (rowNum == 1)
 {

 for (int i = 0; i < columnValue.length; i++)
 comparedColumn[i] = columnValue[i];
 }

 for (int i = 0; i < columnValue.length; i++)
 {

 if (!comparedColumn[i].equals(columnValue[i]))
 {
 for (int j = 0; j < columnValue.length; j++)
 {
 comparedColumn[j] = columnValue[j];
 }
 rowNum = 1;
 return rowNum++;
 }
 }
 return rowNum++;
 }
}

Hive应用:

hive>add jar /home/work/local/hive/udf/row_number.jar;
create temporary function row_number as 'com.baifendian.hive.udf.RowNumber';
select *,row_number(col1,col2,col3)
from (
select col1,col2,col3
from tab
order by col1,col2,col3)a;

 

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