Hive custom User Defined Function(UDF)

Hive supports plenty of built-in SQL-like functions in HiveQL. But just in case, if there is a need to write our own UDF, we can write the same in Java.

Implementation steps

1. Create a Java class for User Defined Function by extending org.apache.hadoop.hive.ql.exec.UDF class and implement one or more evaluate() methods and put our desired logic in that method.
2. Package Java class into JAR file.
3. Go to Hive CLI – ADD the packaged JAR using ADD JAR command.
4. CREATE TEMPORARY FUNCTION in hive which points to the custom UDF Java class.
5. Use this function in a regular Hive query.

System Requirements:

• Operating System : Any(Windows/Linux/Mac)
• Java : JDK1.8
• Build Tool: Maven
• IDE used: Eclipse

Compile

mvn compile

Test

mvn test

Package

mvn clean package

Run

%> hive
hive> ADD JAR /home/sakthiinfotec/hive-custom-udfs-0.0.1-SNAPSHOT.jar;
hive> CREATE TEMPORARY FUNCTION toUpperCase as 'com.sakthiinfotec.hive.custom.ToUpperCaseUDF';
hive> SELECT toUpperCase(first_name) FROM users LIMIT 25;