Hive is built on top of Hadoop, which is a distributed file system and a framework for processing large data sets. Hive supports external functions, which allow users to extend the functionality of Hive by adding their own custom functions. In this article, we will discuss the role of Hive external functions and how to use them.
Role of Hive External Functions:
External functions in Hive are user-defined functions that can be used in Hive queries. These functions allow users to extend the functionality of Hive by providing additional processing capabilities that are not available in the standard HiveQL language. Hive external functions are written in programming languages such as Java, Python, or C++ and can be used to process data in various ways. The role of external functions is to provide custom data processing capabilities that are not available in the standard HiveQL language.
Hive external functions are essential in big data processing, as they allow users to customize their data processing logic. This is important because big data processing requires specialized techniques that are not available in standard SQL or HiveQL. External functions provide users with the ability to apply these specialized techniques to their data, thereby improving the accuracy and efficiency of their data analysis.
Using External Functions in Hive:
To use external functions in Hive, you need to create a custom function and register it in Hive. The following steps describe how to create and use an external function in Hive:
- Write the code for the external function in a programming language such as Java, Python, or C++. The code should implement the functionality you want the function to perform.
- Compile the code and create a jar or file that contains the function.
- Upload the jar or file to a location accessible to Hive.
- Use the CREATE FUNCTION statement to register the function in Hive. The statement should specify the name of the function, the path to the jar or file containing the function, and any other parameters required by the function.
- Use the registered function in Hive queries by calling it in the SELECT or WHERE clause of a query. The function can be used just like any other built-in function in Hive.
For example, suppose you have a Java function that calculates the square of a number. To use this function in Hive, you would follow these steps:
- Write the Java code for the function that calculates the square of a number:
public class MyFunctions {
public static double square(double num) {
return num * num;
}
}
- Compile the code and create a jar file called MyFunctions.jar.
- Upload the jar file to a location accessible to Hive.
- Use the CREATE FUNCTION statement to register the function in Hive:
CREATE FUNCTION square AS 'MyFunctions.square' USING JAR 'MyFunctions.jar';
- Use the registered function in Hive queries:
SELECT square(5);
This query would return the value 25, which is the square of 5.
Hive external functions play an important role in big data processing by allowing users to extend the functionality of Hive with custom data processing capabilities. To use external functions in Hive, you need to create a custom function and register it in Hive using the CREATE FUNCTION statement. Once registered, the function can be used in Hive queries just like any other built-in function.
Hive important pages to refer
