Hive UDFHive UDFs

本文介绍如何创建 Hive UDF、在 Spark 中注册它以及在 Spark SQL 查询中使用它。This article shows how to create a Hive UDF, register it in Spark, and use it in a Spark SQL query.

下面是一个 Hive UDF,它采用 long 作为参数并返回其十六进制表示形式。Here is a Hive UDF that takes a long as an argument and returns its hexadecimal representation.

import org.apache.hadoop.hive.ql.exec.UDF
import org.apache.hadoop.io.LongWritable

// This UDF takes a long integer and converts it to a hexadecimal string.

class ToHex extends UDF {
  def evaluate(n: LongWritable): String = {
    Option(n)
    .map { num =>
        // Use Scala string interpolation. It's the easiest way, and it's
        // type-safe, unlike String.format().
        f"0x${num.get}%x"
    }
    .getOrElse("")
  }
}

注册函数:Register the function:

spark.sql("CREATE TEMPORARY FUNCTION to_hex AS 'com.ardentex.spark.hiveudf.ToHex'")

将函数用作任何其他已注册的函数:Use your function as any other registered function:

spark.sql("SELECT first_name, to_hex(code) as hex_code FROM people")

可以在示例 Hive UDF 项目中找到更多示例和可编译代码。You can find more examples and compilable code at Sample Hive UDF project.