正如我在Spark Dataframe中所知,多列的名称可以与下面的数据帧快照中显示的名称相同:
[
Row(a=107831, f=SparseVector(5, {0: 0.0, 1: 0.0, 2: 0.0, 3: 0.0, 4: 0.0}), a=107831, f=SparseVector(5, {0: 0.0, 1: 0.0, 2: 0.0, 3: 0.0, 4: 0.0})),
Row(a=107831, f=SparseVector(5, {0: 0.0, 1: 0.0, 2: 0.0, 3: 0.0, 4: 0.0}), a=125231, f=SparseVector(5, {0: 0.0, 1: 0.0, 2: 0.0047, 3: 0.0, 4: 0.0043})),
Row(a=107831, f=SparseVector(5, {0: 0.0, 1: 0.0, 2: 0.0, 3: 0.0, 4: 0.0}), a=145831, f=SparseVector(5, {0: 0.0, 1: 0.2356, 2: 0.0036, 3: 0.0, 4: 0.4132})),
Row(a=107831, f=SparseVector(5, {0: 0.0, 1: …来自spark-sql的这个例子中的列名来自case class Person.
case class Person(name: String, age: Int)
val people: RDD[Person] = ... // An RDD of case class objects, from the previous example.
// The RDD is implicitly converted to a SchemaRDD by createSchemaRDD, allowing it to be stored using Parquet.
people.saveAsParquetFile("people.parquet")
https://spark.apache.org/docs/1.1.0/sql-programming-guide.html
但是,在许多情况下,参数名称可能会更改.如果文件尚未更新以反映更改,则会导致找不到列.
如何指定适当的映射？
我想的是:
val schema = StructType(Seq(
StructField("name", StringType, nullable = false),
StructField("age", IntegerType, nullable = false)
))
val ps: Seq[Person] = ???
val personRDD = sc.parallelize(ps)
// Apply the schema to the …