udf没有TypeTag可用于类型字符串 [英] udf No TypeTag available for type string
问题描述
我不了解火花的行为.
I don't understand a behavior of spark.
我创建了一个udf,返回如下所示的整数
I create an udf wich return an Integer like below
import org.apache.spark.sql.SQLContext
import org.apache.spark.{SparkConf, SparkContext}
object Show {
def main(args: Array[String]): Unit = {
val (sc,sqlContext) = iniSparkConf("test")
val testInt_udf = sqlContext.udf.register("testInt_udf", testInt _)
}
def iniSparkConf(appName: String): (SparkContext, SQLContext) = {
val conf = new SparkConf().setAppName(appName)//.setExecutorEnv("spark.ui.port", "4046")
val sc = new SparkContext(conf)
sc.setLogLevel("WARN")
val sqlContext = new SQLContext(sc)
(sc, sqlContext)
}
def testInt() : Int= {
return 2
}
}
我工作得很好,但是如果我将方法测试的返回类型从Int更改为String
I work perfectly but if I change the return type of method test from Int to String
val testString_udf = sqlContext.udf.register("testString_udf", testString _)
def testString() : String = {
return "myString"
}
我收到以下错误
Error:(34, 43) No TypeTag available for String
val testString_udf = sqlContext.udf.register("testString_udf", testString _)
Error:(34, 43) not enough arguments for method register: (implicit evidence$1: reflect.runtime.universe.TypeTag[String])org.apache.spark.sql.UserDefinedFunction.
Unspecified value parameter evidence$1.
val testString_udf = sqlContext.udf.register("testString_udf", testString _)
这是我的嵌入式jars
here are my embedded jars:
datanucleus-api-jdo-3.2.6
datanucleus-core-3.2.10
datanucleus-rdbms-3.2.9
spark-1.6.1-yarn-shuffle
spark-assembly-1.6.1-hadoop2.6.0
spark-examples-1.6.1-hadoop2.6.0
我有点迷路了...你有什么主意吗?
I am a little bit lost... Do you have any idea?
推荐答案
由于我无法复制仅将示例代码复制粘贴到新文件中的问题,所以我敢打赌,在您的真实代码中String
实际上被遮盖了通过别的东西.要验证这一理论,您可以尝试将您的签名更改为
Since I can't reproduce the issue copy-pasting just your example code into a new file, I bet that in your real code String
is actually shadowed by something else. To verify this theory you can try to change you signature to
def testString() : scala.Predef.String = {
return "myString"
}
或
def testString() : java.lang.String = {
return "myString"
}
如果此版本可编译,请搜索字符串"以查看如何隐藏标准类型.如果您使用IntelliJ Idea,则可以尝试使用"Ctrl + B"(转到)找出来.最明显的候选人是您使用String
作为泛型类型参数的名称,但可能还有其他选择.
If this one compiles, search for "String" to see how you shadowed the standard type. If you use IntelliJ Idea, you can try to use "Ctrl+B" (GoTo) to find it out. The most obvious candidate is that you used String
as a name of generic type parameter but there might be some other choices.
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