Spark 2 Dataset Null值异常

在spark Dataset.filter中获取此null错误

输入CSV:

name,age,stat
abc,22,m
xyz,,s

工作代码:

case class Person(name: String, age: Long, stat: String)

val peopleDS = spark.read.option("inferSchema","true")
  .option("header", "true").option("delimiter", ",")
  .csv("./people.csv").as[Person]
peopleDS.show()
peopleDS.createOrReplaceTempView("people")
spark.sql("select * from people where age > 30").show()

失败的代码(添加以下行返回错误):

val filteredDS = peopleDS.filter(_.age > 30)
filteredDS.show()

返回null错误

java.lang.RuntimeException: Null value appeared in non-nullable field:
- field (class: "scala.Long", name: "age")
- root class: "com.gcp.model.Person"
If the schema is inferred from a Scala tuple/case class, or a Java bean, please try to use scala.Option[_] or other nullable types (e.g. java.lang.Integer instead of int/scala.Int).

user6910411.. 19

你得到的例外应该解释一切,但让我们一步一步走:

使用csv数据源加载数据时,所有字段都标记为nullable:

val path: String = ???

val peopleDF = spark.read
  .option("inferSchema","true")
  .option("header", "true")
  .option("delimiter", ",")
  .csv(path)

peopleDF.printSchema

root
|-- name: string (nullable = true)
|-- age: integer (nullable = true)
|-- stat: string (nullable = true)

peopleDF.where($"age".isNull).show

+----+----+----+
|name| age|stat|
+----+----+----+
| xyz|null|   s|
+----+----+----+

val peopleDS = peopleDF.as[Person]

peopleDS.printSchema

root
 |-- name: string (nullable = true)
 |-- age: integer (nullable = true)
 |-- stat: string (nullable = true)

peopleDS.where($"age" > 30).show

+----+---+----+
|name|age|stat|
+----+---+----+
+----+---+----+

peopleDS.filter(_.age > 30)

case class Person(name: String, age: Option[Long], stat: String)

peopleDS.filter(_.age.map(_ > 30).getOrElse(false))

+----+---+----+
|name|age|stat|
+----+---+----+
+----+---+----+

peopleDS.filter {
  case Some(age) => age > 30
  case _         => false     // or case None => false
}

val path: String = ???

val peopleDF = spark.read
  .option("inferSchema","true")
  .option("header", "true")
  .option("delimiter", ",")
  .csv(path)

peopleDF.printSchema

root
|-- name: string (nullable = true)
|-- age: integer (nullable = true)
|-- stat: string (nullable = true)

peopleDF.where($"age".isNull).show

+----+----+----+
|name| age|stat|
+----+----+----+
| xyz|null|   s|
+----+----+----+

val peopleDS = peopleDF.as[Person]

peopleDS.printSchema

root
 |-- name: string (nullable = true)
 |-- age: integer (nullable = true)
 |-- stat: string (nullable = true)

peopleDS.where($"age" > 30).show

+----+---+----+
|name|age|stat|
+----+---+----+
+----+---+----+

peopleDS.filter(_.age > 30)

case class Person(name: String, age: Option[Long], stat: String)

peopleDS.filter(_.age.map(_ > 30).getOrElse(false))

+----+---+----+
|name|age|stat|
+----+---+----+
+----+---+----+

peopleDS.filter {
  case Some(age) => age > 30
  case _         => false     // or case None => false
}