如何在 Spark 数据集中存储嵌套的自定义对象? [英] How to store nested custom objects in Spark Dataset?

问题描述

问题是如何在Dataset中存储自定义对象的后续问题?

Spark 版本:3.0.1

Spark version: 3.0.1

可以实现非嵌套自定义类型:

Non-nested custom type is achievable:

import spark.implicits._
import org.apache.spark.sql.{Encoder, Encoders}

class AnObj(val a: Int, val b: String)

implicit val myEncoder: Encoder[AnObj] = Encoders.kryo[AnObj] 

val d = spark.createDataset(Seq(new AnObj(1, "a")))

d.printSchema
root
 |-- value: binary (nullable = true)

但是，如果自定义类型嵌套在product类型(即case class)中，则会报错:

However, if the custom type is nested inside a product type (i.e. case class), it gives an error:

java.lang.UnsupportedOperationException:未找到 InnerObj 的编码器

java.lang.UnsupportedOperationException: No Encoder found for InnerObj

import spark.implicits._
import org.apache.spark.sql.{Encoder, Encoders}

class InnerObj(val a: Int, val b: String)
case class MyObj(val i: Int, val j: InnerObj)

implicit val myEncoder: Encoder[InnerObj] = Encoders.kryo[InnerObj] 

// error
val d = spark.createDataset(Seq(new MyObj(1, new InnerObj(0, "a"))))
// it gives Runtime error: java.lang.UnsupportedOperationException: No Encoder found for InnerObj

我们如何创建带有嵌套自定义类型的Dataset?

How can we create Dataset with nested custom type?

推荐答案

为 MyObj 和 InnerObj 添加编码器应该可以使其工作.

Adding the encoders for both MyObj and InnerObj should make it work.

  class InnerObj(val a:Int, val b: String)
  case class MyObj(val i: Int, j: InnerObj)

  implicit val myEncoder: Encoder[InnerObj] = Encoders.kryo[InnerObj]
  implicit val objEncoder: Encoder[MyObj] = Encoders.kryo[MyObj]

上面的代码片段编译并运行良好

The above snippet compile and run fine

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