HIVE udf之 计算行号

package com.yulong.udf;

import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.ql.udf.UDFType;
@UDFType(deterministic = false)
public class RowNum 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++;
	        }
	
}