Hive的函数

Hive函数分类

函数的定义和java、mysql一样，有三种。

UDF（User Definition Function 用户定义函数）

一路输入，一路输出
sin(30°)=1/2

UDAF（User Definition Aggregation Function 聚合函数）

多路输入，一路输出
max min count sum avg等等

UDTF（User Definition Table Function 表函数）

一路输入，多路输出
explode

常用函数

show functions;             列出hive中可用的函数列表
desc function func_name;    查看函数的帮助说明

case when   ---->switch或if else
if          ---->三元运算符
explode     ---->将数组中的元素转换成多行数据
a = [1, 2, 3, 4] explode(a) ===>
        1
        2
        3
        4
split       ---->就是字符串中的split函数

array       ---->
collect_set
collect_list
concat_ws   ---->使用给定的字符串来连接元素
--------------
row_number  ---->分组排序或者二次排序

函数案例

wordcount

分析：
    hello   you
    hello   me
    hello   he
使用mr的的过程
    step1----->split("\t")--->
        ["hello", "you"]
        ["hello", "me"]
        ["hello", "he"]
    step2----->遍历每一个数组，将数组中的每一个值，作为key，value为1写出去<key, 1>
        <"hello", 1>
        <"you", 1>
        <"hello", 1>
        <"me", 1>
        <"hello", 1>
        <"he", 1>

    step3,shuffle--->
        <"hello", [1, 1, 1]>
        <"you", 1>
        <"me", 1>
        <"he", 1>
    step 4, reduce ====>reduceByKey
使用hql
    step 1 (mydb1)> select split(line, "\t") from test;
            ["hello","you"]
            ["hello","he"]
            ["hello","me"]
    step 2 将数组中的每一行数据转化为多行
            (mydb1)> select explode(split(line, "\t"))  from test;
                hello
                you
                hello
                he
                hello
                me
    step 3 在step2的基础之上进行group by 即可
        select
            w.word, count(w.word) as count 
        from (select explode(split(line, "\t")) word  from test) w
        group by w.word order by count desc;

case when

case when将一下对应的部门名称显示出来：

1--->学工组，2--->行政组,3---->销售组,4---->研发组,5---->其它
hive (mydb1)> select * from t1;
1
2
3
4
5
select
  id,
case id
  when 1 then "学工组"
  when 2 then "行政组"
  when 3 then "销售组"
  when 4 then "研发组"
  else "行政组"
end
from t1;    
分类显示
1   学工组
2   行政组
3   销售组
4   研发组
5   其它

row_number 二次排序

三种连接
    交叉连接
        across join，会有笛卡尔积，所以不用
    内连接(等值连接)
        inner join
        将左表和右表中能够匹配的上的数据做输出
    外链接
        outer join
        左外连接(left outer join)

        右外链接(right outer join)

根据员工、部分、薪资，这三张表，
    1、分组显示每一个部分员工的信息（启动显示部分名称，员工姓名，员工性别[男|女]，员工薪资），同时分组按照员工薪资降序排序
        select
           e.name, if(sex == 0, '女', '男') as gender, d.name, s.salary,
           row_number() over(partition by e.deptid order by s.salary desc) rank
        from t_dept d
        left join t_employee e on d.id = e.deptid
        left join t_salary s on e.id = s.empid
        where s.salary is not null;
    2、获取显示部门薪资top2的员工信息
        select 
           tmp.* 
        from 
        (select
           e.name, if(sex == 0, '女', '男') as gender, d.name, s.salary, 
           row_number() over(partition by e.deptid order by s.salary desc) rank 
        from t_dept d
        left join t_employee e on d.id = e.deptid
        left join t_salary s on e.id = s.empid
        where s.salary is not null) tmp
        where tmp.rank < 3; 
        如果查询的是单表，则可以不用子查询，只用用having来获取即可(having rank < 3)

直接看下面的一个例子就可以知道row_number的使用方法了：

hive (mydb2)> create table t9(
            >   id int,
            >   province string,
            >   salary float
            > );
hive (mydb2)> insert into t9 values(1,'gd',18000),(2,'gd',16000),(3,'bj',13000),(4,'gd',15000),(5,'bj',17000),(6,'bj',19000);
hive (mydb2)> select * from t9;
OK
1       gd      18000.0
2       gd      16000.0
3       bj      13000.0
4       gd      15000.0
5       bj      17000.0
6       bj      19000.0
Time taken: 0.097 seconds, Fetched: 6 row(s)
hive (mydb2)> select
            >   id,
            >   province,
            >   salary,
            >   row_number() over(partition by province order by salary desc) as rank
            > from t9;
OK
6       bj      19000.0 1
5       bj      17000.0 2
3       bj      13000.0 3
1       gd      18000.0 1
2       gd      16000.0 2
4       gd      15000.0 3
Time taken: 1.578 seconds, Fetched: 6 row(s)

Hive自定义函数

自定义函数步骤

自定义函数需要遵循的6个步骤：

1°、自定义一个Java类来继承UDF类
2°、覆盖其中的evaluate()的函数，有系统去调用
3°、将写好的程序打成一个jar，上传至服务器
4°、将3°中的jar加载到hive的classpath
hive终端执行add jar jar_path;
5°、给自定义函数设置一个临时的名称，也就是说要创建一个临时的函数
create temporary function 函数名 as '写的evalutor所在类的全类名';
6°、执行函数结束之后，可以手动销毁临时函数，或者不用管，因为当前会话消失，函数自动销毁

UDF案例：要根据用户的birthday，统计对应的×××和星座

程序代码如下：

package com.uplooking.bigdata.hive.udf;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

@Description(name = "z_c",
        value = "_FUNC_(param1, param2) - 返回给定日期对应的×××或者星座",
        extended = "param1,param2参数可以是一下:\n"
                + "1. param1 is A string in the format of 'yyyy-MM-dd HH:mm:ss' or 'yyyy-MM-dd'.\n"
                + "2. param1 date value\n"
                + "3. param1 timestamp value\n"
                + "3. param2 0 or 1, 0 means constellation， 1 means zodica\n"
                + "Example:\n "
                + "  > SELECT _FUNC_('2009-07-30', 0) FROM src LIMIT 1;\n" + "  狮子座")
public class ZodicaAndConstellationUDF extends UDF {

    public Text evaluate(java.sql.Date date, int type) {
        if(type == 0) {//星座
            return new Text(getConstellation(new Date(date.getTime())));
        } else if(type == 1) { //×××
            return new Text(getZodica(new Date(date.getTime())));
        }
        return null;
    }

    public String[] zodiacArr = { "猴", "鸡", "狗", "猪", "鼠", "牛", "虎", "兔", "龙", "蛇", "马", "羊" };
    public String[] constellationArr = { "水瓶座", "双鱼座", "白羊座", "金牛座", "双子座", "巨蟹座", "狮子座", "×××座", "天秤座", "天蝎座", "射手座", "魔羯座" };
    public int[] constellationEdgeDay = { 20, 19, 21, 21, 21, 22, 23, 23, 23, 23, 22, 22 };
    /**
     * 根据日期获取×××
     * @return
     */
    public String getZodica(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        return zodiacArr[cal.get(Calendar.YEAR) % 12];
    }
    /**
     * 根据日期获取星座
     * @return
     */
    public String getConstellation(Date date) {
        if (date == null) {
            return "";
        }
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int month = cal.get(Calendar.MONTH);
        int day = cal.get(Calendar.DAY_OF_MONTH);
        if (day < constellationEdgeDay[month]) {
            month = month - 1;
        }
        if (month >= 0) {
            return constellationArr[month];
        }
    // default to return 魔羯
        return constellationArr[11];
    }
}

注意依赖在笔记最后面。

上传到服务器后，在hive终端中加载到hive的classpath：

add jar /home/uplooking/jars/hive/udf-zc.jar

自定义函数：

create temporary function zc as 'com.uplooking.bigdata.hive.udf.ZodicaAndConstellationUDF';

创建测试用的临时表：

hive (mydb1)>
            > create temporary table tmp(
            > birthday date);

插入测试用的数据：

hive (mydb1)> insert into tmp values('1994-06-21');

在查询中使用函数：

hive (mydb1)> select zc(birthday,0) from tmp;
OK
c0
双子座
Time taken: 0.084 seconds, Fetched: 1 row(s)
hive (mydb1)> select zc(birthday,1) from tmp;
OK
c0
狗
Time taken: 0.044 seconds, Fetched: 1 row(s)

下面是一个更简单的UDF函数，可以参考进行测试：

package cn.xpleaf.hive.udf;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;

/**
 * @author Leaf
 * @date 2018/9/18 下午11:11
 */
@Description(name = "addUDF", value = "_FUNC_(num1, num2) - 返回给定两个数的和")
public class AddUDF extends UDF {

    public Text evaluate(int num1, int num2) {
        return new Text(String.valueOf(num1 + num2));
    }

}

Hive之jdbc

Hive除了提供前面的cli用户接口，还提供了jdbc的用户接口，但是如果需要使用该接口，则需要先启动hiveserver2服务，启动该服务后，可以通过hive提供的beeline继续以cli的方式操作hive（不过需要注意的是，此时是通过jdbc接口进行操作hive的），也可以通过手工编写java代码来进行操作。

启动hiveserver2服务

[uplooking@uplooking01 ~]$ hiveserver2

通过beeline连接hiveserver进行操作

[uplooking@uplooking01 hive]$ beeline
which: no hbase in (/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/jdk/bin:/home/uplooking/bin:/home/uplooking/app/zookeeper/bin:/home/uplooking/app/hadoop/bin:/home/uplooking/app/hadoop/sbin:/home/uplooking/app/hive/bin)
ls: 无法访问/home/uplooking/app/hive/lib/hive-jdbc-*-standalone.jar: 没有那个文件或目录
Beeline version 2.1.0 by Apache Hive
beeline> !connect jdbc:hive2://uplooking01:10000/mydb1
Connecting to jdbc:hive2://uplooking01:10000/mydb1
Enter username for jdbc:hive2://uplooking01:10000/mydb1: uplooking
Enter password for jdbc:hive2://uplooking01:10000/mydb1: *********
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/uplooking/app/hive/lib/log4j-slf4j-impl-2.4.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/uplooking/app/hadoop/share/hadoop/common/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
Error: Failed to open new session: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: uplooking is not allowed to impersonate uplooking (state=,code=0)

可以看到出现错误，解决方案如下：

在执行JDBC的时候，访问不了远程的Hive的ThriftServer服务
报的错误：uplooking不能伪装为uplooking
    是因为版本在进行升级的时候考虑到的安全策略，需要我们手动对uplooking进行配置，需要将
hadoop中的uplooking用户和hive中的uplooking用户进行打通，配置在$HADOOP_HOME/etc/hadoop/core-site.xml
中进行配置：添加一下配置项
    <property>
        <name>hadoop.proxyuser.uplooking.hosts</name>
        <value>*</value>
        <description>这是uplooking用户访问的本机地址</description>
    </property>
    <property>
        <name>hadoop.proxyuser.uplooking.groups</name>
        <value>root</value>
        <description>代理uplooking设置的组用户</description>
    </property>     
配置成功之后，需要同步到集群中的各个节点，
要想让集群重新加载配置信息，至少hdfs需要重启    

这样之后就可以正常使用beeline通过hive提供的jdbc接口来操作hive了：

beeline> !connect jdbc:hive2://uplooking01:10000/mydb1
Connecting to jdbc:hive2://uplooking01:10000/mydb1
Enter username for jdbc:hive2://uplooking01:10000/mydb1: uplooking
Enter password for jdbc:hive2://uplooking01:10000/mydb1: *********
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/uplooking/app/hive/lib/log4j-slf4j-impl-2.4.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/uplooking/app/hadoop/share/hadoop/common/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
Connected to: Apache Hive (version 2.1.0)
Driver: Hive JDBC (version 2.1.0)
18/03/23 08:00:15 [main]: WARN jdbc.HiveConnection: Request to set autoCommit to false; Hive does not support autoCommit=false.
Transaction isolation: TRANSACTION_REPEATABLE_READ
0: jdbc:hive2://uplooking01:10000/mydb1> show databases;
+----------------+--+
| database_name  |
+----------------+--+
| default        |
| mydb1          |
+----------------+--+
2 rows selected (2.164 seconds)
0: jdbc:hive2://uplooking01:10000/mydb1> show tables;
+-----------+--+
| tab_name  |
+-----------+--+
| t1        |
| t2        |
+-----------+--+
2 rows selected (0.118 seconds)
0: jdbc:hive2://uplooking01:10000/mydb1> select * from t1;
+------------+--+
|  t1.line   |
+------------+--+
| hello you  |
| hello he   |
| hello me   |
+------------+--+
3 rows selected (2.143 seconds)
0: jdbc:hive2://uplooking01:10000/mydb1> 

通过java代码连接hiveserver进行操作

程序代码如下：

package com.uplooking.bigdata.hive.jdbc;

import java.sql.*;

public class HiveJDBC {
    public static void main(String[] args) throws Exception {
        Class.forName("org.apache.hive.jdbc.HiveDriver");
        Connection conn = DriverManager.getConnection("jdbc:hive2://uplooking01:10000/mydb1", "uplooking", "uplooking");
        String sql = "select t.word,count(t.word) as count from (select explode(split(line, ' ')) as word from t1) t group by t.word";
        PreparedStatement ps = conn.prepareStatement(sql);
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            String word = rs.getString("word");
            int count = rs.getInt("count");
            System.out.println(word + "\t" + count);
        }
        rs.close();
        ps.close();
        conn.close();
    }
}

程序执行结果如下：

18/03/23 00:48:16 INFO jdbc.Utils: Supplied authorities: uplooking01:10000
18/03/23 00:48:16 INFO jdbc.Utils: Resolved authority: uplooking01:10000
he  1
hello   3
me  1
you 1

在这个过程中，注意观察hiveserver2终端的输出：

WARNING: Hive-on-MR is deprecated in Hive 2 and may not be available in the future versions. Consider using a different execution engine (i.e. spark, tez) or using Hive 1.X releases.
Query ID = uplooking_20180323084825_63044683-393d-4625-a3c3-b440109c3d70
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks not specified. Estimated from input data size: 1
In order to change the average load for a reducer (in bytes):
  set hive.exec.reducers.bytes.per.reducer=<number>
In order to limit the maximum number of reducers:
  set hive.exec.reducers.max=<number>
In order to set a constant number of reducers:
  set mapreduce.job.reduces=<number>
Starting Job = job_1521765850571_0002, Tracking URL = http://uplooking02:8088/proxy/application_1521765850571_0002/
Kill Command = /home/uplooking/app/hadoop/bin/hadoop job  -kill job_1521765850571_0002
Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 1
2018-03-23 08:48:33,427 Stage-1 map = 0%,  reduce = 0%
2018-03-23 08:48:40,864 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 3.54 sec
2018-03-23 08:48:48,294 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 6.84 sec
MapReduce Total cumulative CPU time: 6 seconds 840 msec
Ended Job = job_1521765850571_0002
MapReduce Jobs Launched: 
Stage-Stage-1: Map: 1  Reduce: 1   Cumulative CPU: 6.84 sec   HDFS Read: 8870 HDFS Write: 159 SUCCESS
Total MapReduce CPU Time Spent: 6 seconds 840 msec
OK

Hive中文注释乱码解决

如果有乱码出现，可以尝试下面的解决方案：

    hive中文注释乱码解决：
    在hive的元数据库中，执行一下脚本
        ALTER TABLE COLUMNS_V2 MODIFY COLUMN COMMENT VARCHAR(256) CHARACTER SET utf8;
        ALTER TABLE TABLE_PARAMS MODIFY COLUMN PARAM_VALUE VARCHAR(4000) CHARACTER SET utf8;
        ALTER TABLE PARTITION_PARAMS MODIFY COLUMN PARAM_VALUE VARCHAR(4000) CHARACTER SET utf8;
        ALTER TABLE PARTITION_KEYS MODIFY COLUMN PKEY_COMMENT VARCHAR(4000) CHARACTER SET utf8;
        ALTER TABLE INDEX_PARAMS MODIFY COLUMN PARAM_VALUE VARCHAR(4000) CHARACTER SET utf8;
    同时将url，加上utf-8
        &useUnicode=true&characterEncoding=UTF-8
          <property>
            <name>javax.jdo.option.ConnectionURL</name>
            <value>jdbc:mysql://uplooking01:3306/hive?createDatabaseIfNotExist=true&useUnicode=true&characterEncoding=UTF-8</value>
          </property>

Hive的maven依赖

<properties>
   <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   <hive-api.version>2.1.0</hive-api.version>
   <hadoop-api.version>2.6.4</hadoop-api.version>
   <hadoop-core.version>1.2.1</hadoop-core.version>
</properties>

<dependencies>
<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.12</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.apache.hadoop</groupId>
  <artifactId>hadoop-common</artifactId>
  <version>${hadoop-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hadoop</groupId>
  <artifactId>hadoop-mapreduce-client-core</artifactId>
  <version>${hadoop-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hadoop</groupId>
  <artifactId>hadoop-core</artifactId>
  <version>${hadoop-core.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-exec</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-serde</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-service</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-metastore</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-common</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-cli</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.hive</groupId>
  <artifactId>hive-jdbc</artifactId>
  <version>${hive-api.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.thrift</groupId>
  <artifactId>libfb303</artifactId>
  <version>0.9.0</version>
</dependency>
</dependencies>