Spark/Scala代码不再在Spark3.x中工作

Question

这在2.x:下运行良好

import org.apache.spark.sql.functions._
import org.apache.spark.sql.{Encoder, Encoders}
import org.apache.spark.sql.expressions.Window
import org.apache.spark.sql.functions.split
import org.apache.spark.sql.functions.broadcast
import org.apache.spark.sql.functions.{lead, lag}
import spark.implicits._
// Gen example data via DF, can come from files, ordering in those files assumed. I.e. no need to sort.
val df = Seq(
("1 February"), ("n"), ("c"), ("b"), 
("2 February"), ("hh"), ("www"), ("e"), 
("3 February"), ("y"), ("s"), ("j"),
("1 March"), ("c"), ("b"), ("x"),
("1 March"), ("c"), ("b"), ("x"),
("2 March"), ("c"), ("b"), ("x"),
("3 March"), ("c"), ("b"), ("x"), ("y"), ("z")
).toDF("line")
// Define Case Classes to avoid Row aspects on df --> rdd --> to DF which I always must look up again.
case class X(line: String)
case class Xtra(key: Long, line: String)
// Add the Seq Num using zipWithIndex.
val rdd = df.as[X].rdd.zipWithIndex().map{case (v,k) => (k,v)}
val ds = rdd.toDF("key", "line").as[Xtra]

最后一条语句现在返回3.x:

AnalysisException: Cannot up cast line from struct<line:string> to string.
The type path of the target object is:
- field (class: "java.lang.String", name: "line")
- root class: "$linecfabb246f6fc445196875da751b278e883.$read.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.Xtra"
You can either add an explicit cast to the input data or choose a higher precision type of the field in the target object

我发现这个信息很难理解，也很难理解改变的原因。我刚刚测试了2.4.5。一切都很好。

Answer 1

由于line被推断为一个结构，您可以稍微更改您的模式(案例类(：

case class X(line: String)
case class Xtra(key: Long, nested_line: X)

然后使用获得所需的结果

val ds = rdd.toDF("key", "nested_line").as[Xtra].select("key", "nested_line.line")