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implicits Object -- Implicits Conversions

implicits object gives <> for converting Scala objects (incl. RDDs) into a Dataset, DataFrame, Columns or supporting such conversions (through <>).

[[methods]] .implicits API [cols="1,2",options="header",width="100%"] |=== | Name | Description

| localSeqToDatasetHolder a| [[localSeqToDatasetHolder]] Creates a <> with the input Seq[T] converted to a Dataset[T] (using <>).

implicit def localSeqToDatasetHolder[T : Encoder](s: Seq[T]): DatasetHolder[T]

| Encoders | [[Encoders]] Encoders for primitive and object types in Scala and Java (aka boxed types)

| StringToColumn a| [[StringToColumn]] Converts $"name" into a Column

[source, scala]

implicit class StringToColumn(val sc: StringContext)

| rddToDatasetHolder a| [[rddToDatasetHolder]]

[source, scala]

implicit def rddToDatasetHolderT : Encoder: DatasetHolder[T]

| symbolToColumn a| [[symbolToColumn]]

[source, scala]

implicit def symbolToColumn(s: Symbol): ColumnName

|===

implicits object is defined inside <> and hence requires that you build a <> instance first before importing implicits conversions.

[source, scala]

import org.apache.spark.sql.SparkSession val spark: SparkSession = ... import spark.implicits._

scala> val ds = Seq("I am a shiny Dataset!").toDS ds: org.apache.spark.sql.Dataset[String] = [value: string]

scala> val df = Seq("I am an old grumpy DataFrame!").toDF df: org.apache.spark.sql.DataFrame = [value: string]

scala> val df = Seq("I am an old grumpy DataFrame with text column!").toDF("text") df: org.apache.spark.sql.DataFrame = [text: string]

val rdd = sc.parallelize(Seq("hello, I'm a very low-level RDD")) scala> val ds = rdd.toDS ds: org.apache.spark.sql.Dataset[String] = [value: string]


[TIP]

In Scala REPL-based environments, e.g. spark-shell, use :imports to know what imports are in scope.

[source, scala]

scala> :help imports

show import history, identifying sources of names

scala> :imports 1) import org.apache.spark.SparkContext._ (69 terms, 1 are implicit) 2) import spark.implicits._ (1 types, 67 terms, 37 are implicit) 3) import spark.sql (1 terms) 4) import org.apache.spark.sql.functions._ (354 terms)


implicits object extends SQLImplicits abstract class.

=== [[DatasetHolder]][[toDS]][[toDF]] DatasetHolder Scala Case Class

[[ds]] [[creating-instance]] DatasetHolder is a Scala case class that, when created, takes a Dataset[T].

DatasetHolder is <> (implicitly) when <> and <> implicit conversions are used.

DatasetHolder has toDS and toDF methods that simply return the <> (it was created with) or a DataFrame (using <> operator), respectively.

[source, scala]

toDS(): Dataset[T] toDF(): DataFrame toDF(colNames: String*): DataFrame


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