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added kotlin-spark-api-less example for spark as well
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‎examples/README.md

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* [json](idea-examples/json) Using OpenAPI support in DataFrame's Gradle and KSP plugins to access data from [API guru](https://apis.guru/) in a type-safe manner
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* [imdb sql database](https://github.com/zaleslaw/KotlinDataFrame-SQL-Examples) This project prominently showcases how to convert data from an SQL table to a Kotlin DataFrame
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and how to transform the result of an SQL query into a DataFrame.
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* [unsupported-data-sources](idea-examples/unsupported-data-sources) Showcases of how to use DataFrame with
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(momentarily) unsupported data libraries such as [Spark](https://spark.apache.org/) and [Exposed](https://github.com/JetBrains/Exposed).
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They show how to convert to and from Kotlin Dataframe and their respective tables.
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* **JetBrains Exposed**: See the [exposed folder](./idea-examples/unsupported-data-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/examples/exposed)
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for an example of using Kotlin Dataframe with [Exposed](https://github.com/JetBrains/Exposed).
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* **Apache Spark**: See the [spark folder](./idea-examples/unsupported-data-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/examples/spark)
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for an example of using Kotlin Dataframe with [Spark](https://spark.apache.org/).
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* **Spark (with Kotlin Spark API)**: See the [kotlinSpark folder](./idea-examples/unsupported-data-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/examples/kotlinSpark)
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for an example of using Kotlin DataFrame with the [Kotlin Spark API](https://github.com/JetBrains/kotlin-spark-api).
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### Notebook examples
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‎examples/idea-examples/unsupported-data-sources/build.gradle.kts

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@@ -1,6 +1,3 @@
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import org.jetbrains.kotlin.gradle.dsl.JvmTarget
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import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
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plugins {
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application
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kotlin("jvm")
@@ -52,3 +49,21 @@ val runKotlinSparkUntypedDataset by tasks.registering(JavaExec::class) {
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javaLauncher = javaToolchains.launcherFor { languageVersion = JavaLanguageVersion.of(11) }
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mainClass = "org.jetbrains.kotlinx.dataframe.examples.kotlinSpark.UntypedDatasetKt"
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}
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/**
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* Runs the spark/typedDataset example with java 11.
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*/
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val runSparkTypedDataset by tasks.registering(JavaExec::class) {
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classpath = sourceSets["main"].runtimeClasspath
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javaLauncher = javaToolchains.launcherFor { languageVersion = JavaLanguageVersion.of(11) }
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mainClass = "org.jetbrains.kotlinx.dataframe.examples.spark.TypedDatasetKt"
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}
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/**
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* Runs the spark/untypedDataset example with java 11.
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*/
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val runSparkUntypedDataset by tasks.registering(JavaExec::class) {
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classpath = sourceSets["main"].runtimeClasspath
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javaLauncher = javaToolchains.launcherFor { languageVersion = JavaLanguageVersion.of(11) }
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mainClass = "org.jetbrains.kotlinx.dataframe.examples.spark.UntypedDatasetKt"
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}

‎examples/idea-examples/unsupported-data-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/examples/kotlinSpark/compatibilityLayer.kt

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package org.jetbrains.kotlinx.dataframe.examples.kotlinSpark
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import org.apache.spark.api.java.JavaSparkContext
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import org.apache.spark.sql.Dataset
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import org.apache.spark.sql.Row
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import org.apache.spark.sql.RowFactory
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import org.apache.spark.sql.SparkSession
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import org.apache.spark.sql.types.ArrayType
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import org.apache.spark.sql.types.DataType
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import org.apache.spark.sql.types.DataTypes
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import org.apache.spark.sql.types.Decimal
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import org.apache.spark.sql.types.DecimalType
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import org.apache.spark.sql.types.MapType
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import org.apache.spark.sql.types.StructType
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import org.apache.spark.unsafe.types.CalendarInterval
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import org.jetbrains.kotlinx.dataframe.AnyFrame
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import org.jetbrains.kotlinx.dataframe.DataColumn
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import org.jetbrains.kotlinx.dataframe.DataFrame
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import org.jetbrains.kotlinx.dataframe.DataRow
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import org.jetbrains.kotlinx.dataframe.api.rows
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import org.jetbrains.kotlinx.dataframe.api.schema
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import org.jetbrains.kotlinx.dataframe.api.toDataFrame
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import org.jetbrains.kotlinx.dataframe.columns.ColumnGroup
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import org.jetbrains.kotlinx.dataframe.columns.TypeSuggestion
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import org.jetbrains.kotlinx.dataframe.schema.ColumnSchema
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import org.jetbrains.kotlinx.dataframe.schema.DataFrameSchema
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import org.jetbrains.kotlinx.spark.api.toRDD
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import java.math.BigDecimal
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import java.math.BigInteger
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import java.sql.Date
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import java.sql.Timestamp
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import java.time.Instant
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import java.time.LocalDate
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import kotlin.reflect.KType
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import kotlin.reflect.KTypeProjection
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import kotlin.reflect.full.createType
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import kotlin.reflect.full.isSubtypeOf
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import kotlin.reflect.full.withNullability
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import kotlin.reflect.typeOf
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// region Spark to DataFrame
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/**
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* Converts an untyped Spark [Dataset] (Dataframe) to a Kotlin [DataFrame].
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* [StructTypes][StructType] are converted to [ColumnGroups][ColumnGroup].
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*
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* DataFrame supports type inference to do the conversion automatically.
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* This is usually fine for smaller data sets, but when working with larger datasets a type map might be a good idea.
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* See [convertToDataFrame] for more information.
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*/
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fun Dataset<Row>.convertToDataFrameByInference(
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schema: StructType = schema(),
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prefix: List<String> = emptyList(),
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): AnyFrame {
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val columns = schema.fields().map { field ->
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val name = field.name()
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when (val dataType = field.dataType()) {
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is StructType ->
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DataColumn.createColumnGroup(
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name = name,
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df = convertToDataFrameByInference(dataType, prefix + name),
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)
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else ->
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DataColumn.createByInference(
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name = name,
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values = select((prefix + name).joinToString("."))
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.collectAsList()
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.map { it[0] },
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suggestedType = TypeSuggestion.Infer,
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nullable = field.nullable(),
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)
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}
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}
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return columns.toDataFrame()
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}
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/**
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* Converts an untyped Spark [Dataset] (Dataframe) to a Kotlin [DataFrame].
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* [StructTypes][StructType] are converted to [ColumnGroups][ColumnGroup].
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*
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* This version uses a [type-map][DataType.convertToDataFrame] to convert the schemas with a fallback to inference.
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* For smaller data sets, inference is usually fine too.
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* See [convertToDataFrameByInference] for more information.
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*/
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fun Dataset<Row>.convertToDataFrame(schema: StructType = schema(), prefix: List<String> = emptyList()): AnyFrame {
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val columns = schema.fields().map { field ->
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val name = field.name()
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when (val dataType = field.dataType()) {
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is StructType ->
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DataColumn.createColumnGroup(
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name = name,
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df = convertToDataFrame(dataType, prefix + name),
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)
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else ->
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DataColumn.createByInference(
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name = name,
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values = select((prefix + name).joinToString("."))
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.collectAsList()
101-
.map { it[0] },
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suggestedType =
103-
dataType.convertToDataFrame()
104-
?.let(TypeSuggestion::Use)
105-
?: TypeSuggestion.Infer, // fallback to inference if needed
106-
nullable = field.nullable(),
107-
)
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}
109-
}
110-
return columns.toDataFrame()
111-
}
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/**
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* Returns the corresponding Kotlin type for a given Spark DataType.
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*
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* This list may be incomplete, but it can at least give you a good start.
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*
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* @return The KType that corresponds to the Spark DataType, or null if no matching KType is found.
119-
*/
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fun DataType.convertToDataFrame(): KType? =
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when {
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this == DataTypes.ByteType -> typeOf<Byte>()
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this == DataTypes.ShortType -> typeOf<Short>()
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this == DataTypes.IntegerType -> typeOf<Int>()
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this == DataTypes.LongType -> typeOf<Long>()
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this == DataTypes.BooleanType -> typeOf<Boolean>()
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this == DataTypes.FloatType -> typeOf<Float>()
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this == DataTypes.DoubleType -> typeOf<Double>()
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@file:Suppress("ktlint:standard:no-empty-file")
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this == DataTypes.StringType -> typeOf<String>()
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this == DataTypes.DateType -> typeOf<Date>()
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this == DataTypes.TimestampType -> typeOf<Timestamp>()
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this is DecimalType -> typeOf<Decimal>()
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this == DataTypes.CalendarIntervalType -> typeOf<CalendarInterval>()
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this == DataTypes.NullType -> nullableNothingType
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this == DataTypes.BinaryType -> typeOf<ByteArray>()
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this is ArrayType -> {
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when (elementType()) {
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DataTypes.ShortType -> typeOf<ShortArray>()
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DataTypes.IntegerType -> typeOf<IntArray>()
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DataTypes.LongType -> typeOf<LongArray>()
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DataTypes.FloatType -> typeOf<FloatArray>()
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DataTypes.DoubleType -> typeOf<DoubleArray>()
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DataTypes.BooleanType -> typeOf<BooleanArray>()
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else -> null
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}
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}
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this is MapType -> {
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val key = keyType().convertToDataFrame() ?: return null
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val value = valueType().convertToDataFrame() ?: return null
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Map::class.createType(
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listOf(
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KTypeProjection.invariant(key),
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KTypeProjection.invariant(value.withNullability(valueContainsNull())),
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),
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)
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}
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else -> null
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}
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// endregion
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// region DataFrame to Spark
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180-
/**
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* Converts the DataFrame to a Spark Dataset of Rows using the provided SparkSession and JavaSparkContext.
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*
183-
* Spark needs both the data and the schema to be converted to create a correct [Dataset].
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*
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* @param spark The SparkSession object to use for creating the DataFrame.
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* @param sc The JavaSparkContext object to use for converting the DataFrame to RDD.
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* @return A Dataset of Rows representing the converted DataFrame.
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*/
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fun DataFrame<*>.convertToSpark(spark: SparkSession, sc: JavaSparkContext): Dataset<Row> {
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val rows = sc.toRDD(rows().map { it.convertToSpark() })
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return spark.createDataFrame(rows, schema().convertToSpark())
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}
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/**
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* Converts a DataRow to a Spark Row object.
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*
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* @return The converted Spark Row.
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*/
199-
fun DataRow<*>.convertToSpark(): Row =
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RowFactory.create(
201-
*values().map {
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when (it) {
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is DataRow<*> -> it.convertToSpark()
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else -> it
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}
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}.toTypedArray(),
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)
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/**
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* Converts a DataFrameSchema to a Spark StructType.
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*
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* @return The converted Spark StructType.
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*/
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fun DataFrameSchema.convertToSpark(): StructType =
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DataTypes.createStructType(
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columns.map { (name, schema) ->
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DataTypes.createStructField(name, schema.convertToSpark(), schema.nullable)
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},
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)
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/**
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* Converts a ColumnSchema object to Spark DataType.
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*
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* @return The Spark DataType corresponding to the given ColumnSchema object.
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* @throws IllegalArgumentException if the column type or kind is unknown.
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*/
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fun ColumnSchema.convertToSpark(): DataType =
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when (this) {
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is ColumnSchema.Value -> type.convertToSpark() ?: error("unknown data type: $type")
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is ColumnSchema.Group -> schema.convertToSpark()
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is ColumnSchema.Frame -> error("nested dataframes are not supported")
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else -> error("unknown column kind: $this")
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}
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package org.jetbrains.kotlinx.dataframe.examples.kotlinSpark
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235-
/**
236-
* Returns the corresponding Spark DataType for a given Kotlin type.
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*
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* This list may be incomplete, but it can at least give you a good start.
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*
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* @return The Spark DataType that corresponds to the Kotlin type, or null if no matching DataType is found.
5+
/*
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* See ../spark/compatibilityLayer.kt for the implementation.
7+
* It's the same with- and without the Kotlin Spark API.
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*/
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fun KType.convertToSpark(): DataType? =
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when {
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isSubtypeOf(typeOf<Byte?>()) -> DataTypes.ByteType
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isSubtypeOf(typeOf<Short?>()) -> DataTypes.ShortType
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isSubtypeOf(typeOf<Int?>()) -> DataTypes.IntegerType
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isSubtypeOf(typeOf<Long?>()) -> DataTypes.LongType
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isSubtypeOf(typeOf<Boolean?>()) -> DataTypes.BooleanType
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isSubtypeOf(typeOf<Float?>()) -> DataTypes.FloatType
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isSubtypeOf(typeOf<Double?>()) -> DataTypes.DoubleType
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isSubtypeOf(typeOf<String?>()) -> DataTypes.StringType
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isSubtypeOf(typeOf<LocalDate?>()) -> DataTypes.DateType
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isSubtypeOf(typeOf<Date?>()) -> DataTypes.DateType
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isSubtypeOf(typeOf<Timestamp?>()) -> DataTypes.TimestampType
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isSubtypeOf(typeOf<Instant?>()) -> DataTypes.TimestampType
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isSubtypeOf(typeOf<Decimal?>()) -> DecimalType.SYSTEM_DEFAULT()
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isSubtypeOf(typeOf<BigDecimal?>()) -> DecimalType.SYSTEM_DEFAULT()
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isSubtypeOf(typeOf<BigInteger?>()) -> DecimalType.SYSTEM_DEFAULT()
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isSubtypeOf(typeOf<CalendarInterval?>()) -> DataTypes.CalendarIntervalType
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isSubtypeOf(nullableNothingType) -> DataTypes.NullType
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isSubtypeOf(typeOf<ByteArray?>()) -> DataTypes.BinaryType
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isSubtypeOf(typeOf<ShortArray?>()) -> DataTypes.createArrayType(DataTypes.ShortType, false)
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isSubtypeOf(typeOf<IntArray?>()) -> DataTypes.createArrayType(DataTypes.IntegerType, false)
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isSubtypeOf(typeOf<LongArray?>()) -> DataTypes.createArrayType(DataTypes.LongType, false)
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isSubtypeOf(typeOf<FloatArray?>()) -> DataTypes.createArrayType(DataTypes.FloatType, false)
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isSubtypeOf(typeOf<DoubleArray?>()) -> DataTypes.createArrayType(DataTypes.DoubleType, false)
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isSubtypeOf(typeOf<BooleanArray?>()) -> DataTypes.createArrayType(DataTypes.BooleanType, false)
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isSubtypeOf(typeOf<Array<*>>()) ->
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error("non-primitive arrays are not supported for now, you can add it yourself")
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isSubtypeOf(typeOf<List<*>>()) -> error("lists are not supported for now, you can add it yourself")
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isSubtypeOf(typeOf<Set<*>>()) -> error("sets are not supported for now, you can add it yourself")
298-
299-
classifier == Map::class -> {
300-
val (key, value) = arguments
301-
DataTypes.createMapType(
302-
key.type?.convertToSpark(),
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value.type?.convertToSpark(),
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value.type?.isMarkedNullable ?: true,
305-
)
306-
}
307-
308-
else -> null
309-
}
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311-
private val nullableNothingType: KType = typeOf<List<Nothing?>>().arguments.first().type!!
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// endregion

‎examples/idea-examples/unsupported-data-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/examples/kotlinSpark/untypedDataset.kt

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@@ -12,6 +12,9 @@ import org.jetbrains.kotlinx.dataframe.api.min
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import org.jetbrains.kotlinx.dataframe.api.print
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import org.jetbrains.kotlinx.dataframe.api.schema
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import org.jetbrains.kotlinx.dataframe.api.std
15+
import org.jetbrains.kotlinx.dataframe.examples.spark.convertToDataFrame
16+
import org.jetbrains.kotlinx.dataframe.examples.spark.convertToDataFrameByInference
17+
import org.jetbrains.kotlinx.dataframe.examples.spark.convertToSpark
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import org.jetbrains.kotlinx.spark.api.col
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import org.jetbrains.kotlinx.spark.api.gt
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import org.jetbrains.kotlinx.spark.api.withSpark
@@ -20,7 +23,7 @@ import org.jetbrains.kotlinx.spark.api.withSpark
2023
* Since we don't know the schema at compile time this time, we need to do
2124
* some schema mapping in between Spark and DataFrame.
2225
*
23-
* We will use compatibilityLayer.kt to do this.
26+
* We will use spark/compatibilityLayer.kt to do this.
2427
*
2528
* NOTE: You will likely need to run this function with Java 8 or 11 for it to work correctly.
2629
* Use the `runKotlinSparkUntypedDataset` Gradle task to do so.

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