大数据Spark “蘑菇云”行动第93课：Hive中的内置函数、UDF、UDAF实战

 大数据Spark “蘑菇云”行动第93课：Hive中的内置函数、UDF、UDAF实战

select sum_all(age) from ...

hive> use default;

show tables;

select * from employeeforhaving;

一：udf 编码

import org.apache.hadoop.hive.ql.exec.UDF;

import org.apache.hadoop.io.Text;

public final class LowerCase extends UDF {

  public Text evaluate(final Text s) {

    if (s == null) { return null; }

    return new Text(s.toString().toLowerCase());

  }

}

二：导出jar包  hadoopapps.jar

三，加载jar包

hive> add jar /root/..../hadoopapps.jar

四，hive> CREATE TEMPORARY FUNCTION tolower AS com.dt.spark.hive.HIVEUDF 

五，使用

hive> SELECT tolower(name) from employeeforhaving;

一：UDAF 聚合 编码

import org.apache.hadoop.hive.ql.exec.UDAF;

import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;

public class concat extends UDAF {

 public static class ConcatUDAFEvaluator implements UDAFEvaluator{

  public static class PartialResult{

   String result;

   String delimiter;

  }

  private PartialResult partial;

  

  public void init() {

   partial = null;

  }

  

  public boolean iterate(String value,String deli){

   

   if (value == null){

    return true;

   }

   if (partial == null){

    partial = new PartialResult();

    partial.result = new String("");

    if(  deli == null || deli.equals("") )

    {

     partial.delimiter = new String(",");

    }

    else

    {

     partial.delimiter = new String(deli);

    }

        

   }

   if ( partial.result.length() > 0 )

   {

    partial.result = partial.result.concat(partial.delimiter);

   }

   

   partial.result = partial.result.concat(value);

   

   return true;

  }

  

  public PartialResult terminatePartial(){

   return partial;

  }

  

  public boolean merge(PartialResult other){

   if (other == null){

    return true;

   }

   if (partial == null){

    partial = new PartialResult();

    partial.result = new String(other.result);

    partial.delimiter = new String(other.delimiter);

   }

   else

   {   

    if ( partial.result.length() > 0 )

    {

     partial.result = partial.result.concat(partial.delimiter);

    }

    partial.result = partial.result.concat(other.result);

   }

   return true;

  }

  

  public String terminate(){

   return new String(partial.result);

  }

 }

}

二：



















 UDAF 聚合