Merge pull request #217 from huanshankeji/tolist-to-aslist

Replace calls of `toList()` on `Array`s with `asList()` to improve performance of the affected functions by reducing the overhead of copying the array elements for once

Author: Jolanrensen

kotlin-spark-api/src/main/kotlin/org/jetbrains/kotlinx/spark/api/Dataset.kt

@@ -61,19 +61,19 @@ inline fun <reified T> SparkSession.toDF(list: List<T>, vararg colNames: String)
  * Utility method to create dataset from *array or vararg arguments
  */
 inline fun <reified T> SparkSession.dsOf(vararg t: T): Dataset<T> =
-    createDataset(t.toList(), encoder<T>())
+    createDataset(t.asList(), encoder<T>())
 
 /**
  * Utility method to create dataframe from *array or vararg arguments
  */
 inline fun <reified T> SparkSession.dfOf(vararg t: T): Dataset<Row> =
-    createDataset(t.toList(), encoder<T>()).toDF()
+    createDataset(t.asList(), encoder<T>()).toDF()
 
 /**
  * Utility method to create dataframe from *array or vararg arguments with given column names
  */
 inline fun <reified T> SparkSession.dfOf(colNames: Array<String>, vararg t: T): Dataset<Row> =
-    createDataset(t.toList(), encoder<T>())
+    createDataset(t.asList(), encoder<T>())
         .run { if (colNames.isEmpty()) toDF() else toDF(*colNames) }
 
 /**
@@ -92,7 +92,7 @@ inline fun <reified T> List<T>.toDF(spark: SparkSession, vararg colNames: String
  * Utility method to create dataset from list
  */
 inline fun <reified T> Array<T>.toDS(spark: SparkSession): Dataset<T> =
-    toList().toDS(spark)
+    asList().toDS(spark)
 
 /**
  * Utility method to create dataframe from list

kotlin-spark-api/src/main/kotlin/org/jetbrains/kotlinx/spark/api/Rdd.kt

@@ -11,7 +11,7 @@ import java.io.Serializable
 fun <T> JavaSparkContext.rddOf(
     vararg elements: T,
     numSlices: Int = defaultParallelism(),
-): JavaRDD<T> = parallelize(elements.toList(), numSlices)
+): JavaRDD<T> = parallelize(elements.asList(), numSlices)
 
 /**
  * Utility method to create an RDD from a list.

kotlin-spark-api/src/main/kotlin/org/jetbrains/kotlinx/spark/api/SparkSession.kt

@@ -114,7 +114,7 @@ class KSparkSession(val spark: SparkSession) {
      * NOTE: [T] must be [Serializable].
      */
     fun <T> rddOf(vararg elements: T, numSlices: Int = sc.defaultParallelism()): JavaRDD<T> =
-        sc.toRDD(elements.toList(), numSlices)
+        sc.toRDD(elements.asList(), numSlices)
 
     /**
      * A collection of methods for registering user-defined functions (UDF).

kotlin-spark-api/src/test/kotlin/org/jetbrains/kotlinx/spark/api/TypeInferenceTest.kt

@@ -215,7 +215,7 @@ class TypeInferenceTest : ShouldSpec({
         should("generate valid serializer schema") {
             expect(encoder<Sample>().schema()) {
                 this
-                    .feature("data type", { this.fields()?.toList() }) {
+                    .feature("data type", { this.fields()?.asList() }) {
                         this.notToEqualNull().toContain.inOrder.only.entry {
                             this
                                 .feature("element name", { name() }) { toEqual("optionList") }