如何在表达式中使用spark UDF？我有：

def power3(input: Int) = input * input * input

import org.apache.spark.sql.functions.udf
val power3UDF = udf(power3(_:Int):Int).withName("power3UDF")

numDF
  .select(expr("Number"), expr("power3UDF(Number) AS POWER3"))
  .show()

这会产生错误：

Undefined function: power3UDF. This function is neither a built-in/temporary function, nor a persistent function that is qualified as spark_catalog.default.power3udf.