9

私はScalaが初めてです。スカラ リスト (ソース DataFrame で計算されたデータの結果を保持している) を Dataframe または Dataset に変換しようとしています。私はそれを行うための直接的な方法を見つけていません。ただし、リストを DataSet に変換するために次のプロセスを試みましたが、機能していないようです。以下の3つの状況を提供しています。

この変換を行う方法を教えてください。ありがとう。

import org.apache.spark.sql.{DataFrame, Row, SQLContext, DataFrameReader}
import java.sql.{Connection, DriverManager, ResultSet, Timestamp}
import scala.collection._

case class TestPerson(name: String, age: Long, salary: Double)
var tom = new TestPerson("Tom Hanks",37,35.5)
var sam = new TestPerson("Sam Smith",40,40.5)

val PersonList = mutable.MutableList[TestPerson]()

//Adding data in list
PersonList += tom
PersonList += sam

//Situation 1: Trying to create dataset from List of objects:- Result:Error
//Throwing error
var personDS = Seq(PersonList).toDS()
/*
ERROR:
error: Unable to find encoder for type stored in a Dataset.  Primitive types
   (Int, String, etc) and Product types (case classes) are supported by     
importing sqlContext.implicits._  Support for serializing other types will  
be added in future releases.
     var personDS = Seq(PersonList).toDS()

*/
//Situation 2: Trying to add data 1-by-1 :- Result: not working as desired.    
the last record overwriting any existing data in the DS
var personDS = Seq(tom).toDS()
personDS = Seq(sam).toDS()

personDS += sam //not working. throwing error


//Situation 3: Working. However, I am having consolidated data in the list    
which I want to convert to DS; if I loop the results of the list in comma  
separated values and then pass that here, it will work but will create an  
extra loop in the code, which I want to avoid.
var personDS = Seq(tom,sam).toDS()
scala> personDS.show()
+---------+---+------+
|     name|age|salary|
+---------+---+------+
|Tom Hanks| 37|  35.5|
|Sam Smith| 40|  40.5|
+---------+---+------+
4

3 に答える 3

1 
case class TestPerson(name: String, age: Long, salary: Double)

val spark = SparkSession.builder().appName("List to Dataset").master("local[*]").getOrCreate()

var tom = new TestPerson("Tom Hanks",37,35.5)
var sam = new TestPerson("Sam Smith",40,40.5)
   
// mutable.MutableList[TestPerson]() is not required , i used below way which was 
// cleaner
val PersonList =  List(tom,sam)

import spark.implicits._
PersonList.toDS().show
于 2021-07-09T07:01:18.443 に答える
1

シーケンスを使用:

val spark = SparkSession.builder().appName("Spark-SQL").master("local[2]").getOrCreate()

import spark.implicits._

var tom = new TestPerson("Tom Hanks",37,35.5)
var sam = new TestPerson("Sam Smith",40,40.5)

val PersonList = mutable.MutableList[TestPerson]()

//Adding data in list
PersonList += tom
PersonList += sam

//It will be work.
var personDS = Seq(PersonList).toDS()

SQLContext.implicits

于 2020-07-05T03:40:18.117 に答える