Hive Reflect GBK

Hive is a data warehouse infrastructure built on top of Hadoop. It provides a high-level language called HiveQL, which is similar to SQL, to query and analyze data stored in Hadoop Distributed File System (HDFS). However, Hive does not support all the features of SQL out of the box. In some cases, we may need to extend Hive's functionality to meet our specific requirements. One way to achieve this is by using Hive's reflect function with GBK encoding.

What is Hive Reflect GBK?

Reflect is a built-in Hive function that allows us to invoke Java methods within a Hive query. GBK is a character encoding scheme widely used in China. By combining these two, we can leverage the power of Java to extend Hive's functionality and perform tasks that are not natively supported.

How to use Hive Reflect GBK?

To use Hive Reflect GBK, we first need to create a Hive UDF (User-Defined Function) in Java that performs the desired functionality. Let's take an example where we want to convert a string to GBK encoding within a Hive query.

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

import java.io.UnsupportedEncodingException;

public class GBKConverter extends UDF {
  public Text evaluate(Text input) throws UnsupportedEncodingException {
    if (input == null) {
      return null;
    }
    return new Text(new String(input.getBytes(), "GBK"));
  }
}

In the above code, we define a UDF called GBKConverter that takes a Text input and returns a Text output. We use the getBytes() method to convert the input string to bytes and then construct a new string using GBK encoding.

Next, we need to compile the Java code into a JAR file, let's name it hive-reflect-gbk.jar.

Once we have the JAR file, we can register the UDF in Hive using the ADD JAR command:

ADD JAR hive-reflect-gbk.jar;

After the JAR is added, we can create a temporary function in Hive that references the UDF:

CREATE TEMPORARY FUNCTION gbk_convert AS 'com.example.GBKConverter';

Now we can use the gbk_convert function in our Hive queries:

SELECT name, gbk_convert(address) AS gbk_address FROM users;

In the above example, we assume there is a table called users with columns name and address. We use the gbk_convert function to convert the address column to GBK encoding.

Conclusion

Hive Reflect GBK allows us to extend Hive's functionality by invoking Java methods within Hive queries. By creating custom UDFs, we can perform tasks that are not natively supported by Hive. In this article, we discussed how to create a Hive UDF in Java that converts a string to GBK encoding. We also covered how to register the UDF in Hive and use it in queries. Hive Reflect GBK is a powerful feature that enables us to leverage the full potential of Hive and Hadoop ecosystem.