hive是给了我们很多内置函数的，比如转大小写，截取字符串等，具体的都在官方文档里面。但是并不是所有的函数都能满足我们的需求，所以hive提供了给我们自定义函数的功能。
1、至于怎么测试hive为我们提供的函数
因为mysql或者oracle中都可以使用伪表，但是hive不行，所以可以使用以下方法
1）、创建表dual,create table dual(id string)
2）、在本地创建文件dual.data,内容为空格或者空一行
3）、将dual.data文件load到表dual
进行测试，比如：字符串截取
0: jdbc:hive2://localhost:10000> select substr('sichuan',1,3) from dual;
+------+--+
| _c0 |
+------+--+
| sic |
+------+--+当然也可以直接使用 select substr(‘sichuan’,1,3)，但是还是习惯用from dual;
2、自定义内置函数
1）、大写转小写
可以先创建java类继承UDF,重载evaluate方法。
/**
* 大写转小写
* @author 12706
*/
public class UpperToLowerCase extends UDF {
/*
* 重载evaluate
* 访问限制必须是public
*/
public String evaluate(String word) {
String lowerWord = word.toLowerCase();
return lowerWord;
}
}打包上传到hadoop集群（打的jar包名字为hive.jar）。
0: jdbc:hive2://localhost:10000> select * from t5;
+--------+-----------+--+
| t5.id | t5.name |
+--------+-----------+--+
| 13 | BABY |
| 1 | zhangsan |
| 2 | lisi |
| 3 | wangwu |
| 4 | furong |
| 5 | fengjie |
| 6 | aaa |
| 7 | bbb |
| 8 | ccc |
| 9 | ddd |
| 10 | eee |
| 11 | fff |
| 12 | ggg |
+--------+-----------+--+
13 rows selected (0.221 seconds)将jar包放到hive的classpath下
0: jdbc:hive2://localhost:10000> add jar /root/hive.jar;创建临时函数，指定完整类名
0: jdbc:hive2://localhost:10000> create temporary function tolower as 'com.scu.hive.UpperToLowerCase';到这就可以使用自定义临时函数tolower()了，测试t5表中的name输出小写
0: jdbc:hive2://localhost:10000> select id,tolower(name) from t5;
+-----+-----------+--+
| id | _c1 |
+-----+-----------+--+
| 13 | baby |
| 1 | zhangsan |
| 2 | lisi |
| 3 | wangwu |
| 4 | furong |
| 5 | fengjie |
| 6 | aaa |
| 7 | bbb |
| 8 | ccc |
| 9 | ddd |
| 10 | eee |
| 11 | fff |
| 12 | ggg |
+-----+-----------+--+2）、根据电话号码显示归属地信息
jave类
/**
* 根据电话号码前三位获取归属地
* @author 12706
*
*/
public class PhoneNumParse extends UDF{
static HashMap<String, String> phoneMap = new HashMap<String, String>();
static{
phoneMap.put("136", "beijing");
phoneMap.put("137", "shanghai");
phoneMap.put("138", "shenzhen");
}
public static String evaluate(int phoneNum) {
String num = String.valueOf(phoneNum);
String province = phoneMap.get(num.substring(0, 3));
return province==null?"foreign":province;
}
//测试
public static void main(String[] args) {
String string = evaluate(136666);
System.out.println(string);
}
}将工程打包上传到linux，注意：如果名字还是跟上面一样，那么需要重新连接hive服务端了，否则jar包是不会覆盖的，建议打的jar包名字别一样
编辑文件vi prov.data
创建表flow(phonenum int,flow int)
将文件load到flow表
[root@mini1 ~]# vi prov.data;
1367788,1
1367788,10
1377788,80
1377788,97
1387788,98
1387788,99
1387788,100
1555118,990: jdbc:hive2://localhost:10000> create table flow(phonenum int,flow int)
0: jdbc:hive2://localhost:10000> row format delimited fields terminated by ',';
No rows affected (0.143 seconds)
0: jdbc:hive2://localhost:10000> load data local inpath '/root/prov.data' into table flow;
INFO : Loading data to table myhive3.flow from file:/root/prov.data
INFO : Table myhive3.flow stats: [numFiles=1, totalSize=88]
No rows affected (0.316 seconds)
0: jdbc:hive2://localhost:10000> select * from flow;
+----------------+------------+--+
| flow.phonenum | flow.flow |
+----------------+------------+--+
| 1367788 | 1 |
| 1367788 | 10 |
| 1377788 | 80 |
| 1377788 | 97 |
| 1387788 | 98 |
| 1387788 | 99 |
| 1387788 | 100 |
| 1555118 | 99 |
+----------------+------------+--+classpath下加入jar包，创建临时函数，测试
0: jdbc:hive2://localhost:10000> add jar /root/hive.jar;
INFO : Added [/root/hive.jar] to class path
INFO : Added resources: [/root/hive.jar]
No rows affected (0.236 seconds)
0: jdbc:hive2://localhost:10000> create temporary function getprovince as 'com.scu.hive.PhoneNumParse';
No rows affected (0.038 seconds)
0: jdbc:hive2://localhost:10000> select phonenum,getprovince(phonenum),flow from flow;
+-----------+-----------+-------+--+
| phonenum | _c1 | flow |
+-----------+-----------+-------+--+
| 1367788 | beijing | 1 |
| 1367788 | beijing | 10 |
| 1377788 | shanghai | 80 |
| 1377788 | shanghai | 97 |
| 1387788 | shenzhen | 98 |
| 1387788 | shenzhen | 99 |
| 1387788 | shenzhen | 100 |
| 1555118 | foreign | 99 |
+-----------+-----------+-------+--+3）、Json数据解析UDF开发
有文件，内容一部分如下，里面都是json串，现在需要将它展示输出到表中，并解析对应为4个字段。
{"movie":"1193","rate":"5","timeStamp":"978300760","uid":"1"}
{"movie":"661","rate":"3","timeStamp":"978302109","uid":"1"}
{"movie":"914","rate":"3","timeStamp":"978301968","uid":"1"}
{"movie":"3408","rate":"4","timeStamp":"978300275","uid":"1"}
{"movie":"2355","rate":"5","timeStamp":"978824291","uid":"1"}
{"movie":"1197","rate":"3","timeStamp":"978302268","uid":"1"}java类
public class JsonParse extends UDF{
//{"movie":"1193","rate":"5","timeStamp":"978300760","uid":"1"}
//输出字符串 1193 5 978300760 1
public static String evaluate(String line){
ObjectMapper objectMapper = new ObjectMapper();
//json串转java对象
String json = "";
try {
MovieRateBean bean = objectMapper.readValue(line,MovieRateBean.class);
json = bean.toString();
} catch (Exception e) {
e.printStackTrace();
}
return json;
}
}public class MovieRateBean {
private String movie;
private String rate;//评分
private String timeStamp;
private String uid;
@Override
public String toString() {
return this.movie+"\t"+this.rate+"\t"+this.timeStamp+"\t"+this.uid;
}
get、set方法
}工程打包上传到linux下。
创建表json
create table json(line string);
将文件导入到json表
load data local inpath ‘/root/json.data’ into table json;
0: jdbc:hive2://localhost:10000> select * from json limit 10;
+----------------------------------------------------------------+--+
| json.line |
+----------------------------------------------------------------+--+
| {"movie":"1193","rate":"5","timeStamp":"978300760","uid":"1"} |
| {"movie":"661","rate":"3","timeStamp":"978302109","uid":"1"} |
| {"movie":"914","rate":"3","timeStamp":"978301968","uid":"1"} |
| {"movie":"3408","rate":"4","timeStamp":"978300275","uid":"1"} |
| {"movie":"2355","rate":"5","timeStamp":"978824291","uid":"1"} |
| {"movie":"1197","rate":"3","timeStamp":"978302268","uid":"1"} |
| {"movie":"1287","rate":"5","timeStamp":"978302039","uid":"1"} |
| {"movie":"2804","rate":"5","timeStamp":"978300719","uid":"1"} |
| {"movie":"594","rate":"4","timeStamp":"978302268","uid":"1"} |
| {"movie":"919","rate":"4","timeStamp":"978301368","uid":"1"} |
+----------------------------------------------------------------+--+0: jdbc:hive2://localhost:10000> add jar /root/hive3.jar;
INFO : Added [/root/hive3.jar] to class path
INFO : Added resources: [/root/hive3.jar]
No rows affected (0.023 seconds)
0: jdbc:hive2://localhost:10000> create temporary function parsejson as 'com.scu.hive.JsonParse';
No rows affected (0.07 seconds)
0: jdbc:hive2://localhost:10000> select parsejson(line) from json limit 10;
+---------------------+--+
| _c0 |
+---------------------+--+
| 1193 5 978300760 1 |
| 661 3 978302109 1 |
| 914 3 978301968 1 |
| 3408 4 978300275 1 |
| 2355 5 978824291 1 |
| 1197 3 978302268 1 |
| 1287 5 978302039 1 |
| 2804 5 978300719 1 |
| 594 4 978302268 1 |
| 919 4 978301368 1 |
+---------------------+--+到这里发现还有不足的地方，就是没显示字段。可以使用函数来实现重写建表来命名。
0: jdbc:hive2://localhost:10000> create table t_rating as
0: jdbc:hive2://localhost:10000> select split(parsejson(line),'\t')[0]as movieid,
0: jdbc:hive2://localhost:10000> split(parsejson(line),'\t')[1] as rate,
0: jdbc:hive2://localhost:10000> split(parsejson(line),'\t')[2] as timestring,
0: jdbc:hive2://localhost:10000> split(parsejson(line),'\t')[3] as uid
0: jdbc:hive2://localhost:10000> from json limit 10;
...
0: jdbc:hive2://localhost:10000> select * from t_rating;
+-------------------+----------------+----------------------+---------------+--+
| t_rating.movieid | t_rating.rate | t_rating.timestring | t_rating.uid |
+-------------------+----------------+----------------------+---------------+--+
| 919 | 4 | 978301368 | 1 |
| 594 | 4 | 978302268 | 1 |
| 2804 | 5 | 978300719 | 1 |
| 1287 | 5 | 978302039 | 1 |
| 1197 | 3 | 978302268 | 1 |
| 2355 | 5 | 978824291 | 1 |
| 3408 | 4 | 978300275 | 1 |
| 914 | 3 | 978301968 | 1 |
| 661 | 3 | 978302109 | 1 |
| 1193 | 5 | 978300760 | 1 |
+-------------------+----------------+----------------------+---------------+--+transform关键字使用
需求，创建新表，内容与t_rating表一致，但是第三个字段时间戳要改为输出周几。
Hive的 TRANSFORM 关键字提供了在SQL中调用自写脚本的功能
适合实现Hive中没有的功能又不想写UDF的情况。
1、编写python脚本(先看看机器有没有python)，用来将表时间戳转为周几
2、加入编写的py文件
3、创建新表，字段值为t_rating表传入py函数后输出的字段值
[root@mini1 ~]# python
Python 2.6.6 (r266:84292, Feb 21 2013, 23:54:59)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print 'hello';
hello
>>> quit()
[root@mini1 ~]# vi weekday_mapper.py;
#import sys
import datetime
for line in sys.stdin:
line = line.strip()
movieid, rating, unixtime,userid = line.split('\t')
weekday = datetime.datetime.fromtimestamp(float(unixtime)).isoweekday()
print '\t'.join([movieid, rating, str(weekday),userid])切换到hive客户端
0: jdbc:hive2://localhost:10000> add FILE /root/weekday_mapper.py;0: jdbc:hive2://localhost:10000> create TABLE u_data_new as
0: jdbc:hive2://localhost:10000> SELECT
0: jdbc:hive2://localhost:10000> TRANSFORM (movieid, rate, timestring,uid)
0: jdbc:hive2://localhost:10000> USING 'python weekday_mapper.py'
0: jdbc:hive2://localhost:10000> AS (movieid, rate, weekday,uid)
0: jdbc:hive2://localhost:10000> FROM t_rating;
...
0: jdbc:hive2://localhost:10000> select * from u_data_new;
+---------------------+------------------+---------------------+-----------------+--+
| u_data_new.movieid | u_data_new.rate | u_data_new.weekday | u_data_new.uid |
+---------------------+------------------+---------------------+-----------------+--+
| 919 | 4 | 1 | 1 |
| 594 | 4 | 1 | 1 |
| 2804 | 5 | 1 | 1 |
| 1287 | 5 | 1 | 1 |
| 1197 | 3 | 1 | 1 |
| 2355 | 5 | 7 | 1 |
| 3408 | 4 | 1 | 1 |
| 914 | 3 | 1 | 1 |
| 661 | 3 | 1 | 1 |
| 1193 | 5 | 1 | 1 |
+---------------------+------------------+---------------------+-----------------+--+
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