本文共 2260 字，大约阅读时间需要 7 分钟。
大写转小写 package com.afan; import org.apache.hadoop.hive.ql.exec.UDF; import org.apache.hadoop.io.Text; public class UDFLower extends UDF{ public Text evaluate(final Text s){ if (null == s){ return null; } return new Text(s.toString().toLowerCase()); } } 1、加载udf jar包 afan@ubuntu:/usr/local/hadoop/hive$ bin/hive Hive history file=/tmp/afan/hive_job_log_afan_201105150623_175667077.txt hive> add jar udf_hive.jar; Added udf_hive.jar to class path Added resource: udf_hive.jar 2、创建udf函数 hive> create temporary function my_lower as 'com.afan.UDFLower'; OK Time taken: 0.253 seconds 3、创建测试数据 hive> create table dual (info string); OK Time taken: 0.178 seconds hive> load data local inpath 'data.txt' into table dual; Copying data from file:/usr/local/hadoop/hive/data.txt Copying file: file:/usr/local/hadoop/hive/data.txt Loading data to table default.dual OK Time taken: 0.377 seconds hive> select info from dual; Total MapReduce jobs = 1 Launching Job 1 out of 1 Number of reduce tasks is set to 0 since there's no reduce operator Starting Job = job_201105150525_0003, Tracking URL = http://localhost:50030/jobdetails.jsp?jobid=job_201105150525_0003 Kill Command = /usr/local/hadoop/bin/../bin/hadoop job -Dmapred.job.tracker=localhost:9001 -kill job_201105150525_0003 2011-05-15 06:46:05,459 Stage-1 map = 0%, reduce = 0% 2011-05-15 06:46:10,905 Stage-1 map = 100%, reduce = 0% 2011-05-15 06:46:13,963 Stage-1 map = 100%, reduce = 100% Ended Job = job_201105150525_0003 OK WHO AM I HELLO worLd Time taken: 14.874 seconds 4、使用udf函数 hive> select my_lower(info) from dual; Total MapReduce jobs = 1 Launching Job 1 out of 1 Number of reduce tasks is set to 0 since there's no reduce operator Starting Job = job_201105150525_0002, Tracking URL = http://localhost:50030/jobdetails.jsp?jobid=job_201105150525_0002 Kill Command = /usr/local/hadoop/bin/../bin/hadoop job -Dmapred.job.tracker=localhost:9001 -kill job_201105150525_0002 2011-05-15 06:43:26,100 Stage-1 map = 0%, reduce = 0% 2011-05-15 06:43:34,364 Stage-1 map = 100%, reduce = 0% 2011-05-15 06:43:37,484 Stage-1 map = 100%, reduce = 100% Ended Job = job_201105150525_0002 OK who am i hello world Time taken: 20.834 seconds 本文转自 SimplePoint 51CTO博客，原文链接：http://blog.51cto.com/2226894115/1897838，如需转载请自行联系原作者