Hive User Defined Functions (UDF's)

Hive UDF creation

To create a UDF, we need to extend UDF (org.apache.hadoop.hive.ql.exec.UDF) class and implement evaluate method.

Once UDF is complied and JAR is build, we need to add jar to hive context to create a temporary/permanent function.

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

class UDFExample extends UDF {
  
  public String evaluate(String input) {
    
    return new String("Hello " + input);
  }
}

hive> ADD JAR <JAR NAME>.jar;
hive> CREATE TEMPORARY FUNCTION helloworld as 'package.name.UDFExample';
hive> select helloworld(name) from test;

Hive UDF to trim the given string.

package MyHiveUDFs;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;

public class Strip extends UDF {

private Text result = new Text();
 public Text evaluate(Text str) {
 if(str == null) {
 return null;
 }
 result.set(StringUtils.strip(str.toString()));
 return result;
 }
}

export the above to jar file

Go to the Hive CLI and Add the UDF JAR

hive> ADD jar /home/cloudera/Hive/hive_udf_trim.jar;

Verify JAR is in Hive CLI Classpath

hive> list jars;
/home/cloudera/Hive/hive_udf_trim.jar

Create Temporary Function

hive> CREATE TEMPORARY FUNCTION STRIP AS 'MyHiveUDFs.Strip';

UDF Output

 hive> select strip('   hiveUDF ') from dummy;
 OK
 hiveUDF