spark ZippedWithIndexRDD 源码
spark ZippedWithIndexRDD 代码
文件路径：/core/src/main/scala/org/apache/spark/rdd/ZippedWithIndexRDD.scala
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.rdd
import scala.reflect.ClassTag
import org.apache.spark.{Partition, TaskContext}
import org.apache.spark.util.Utils
private[spark]
class ZippedWithIndexRDDPartition(val prev: Partition, val startIndex: Long)
extends Partition with Serializable {
override val index: Int = prev.index
}
/**
* Represents an RDD zipped with its element indices. The ordering is first based on the partition
* index and then the ordering of items within each partition. So the first item in the first
* partition gets index 0, and the last item in the last partition receives the largest index.
*
* @param prev parent RDD
* @tparam T parent RDD item type
*/
private[spark]
class ZippedWithIndexRDD[T: ClassTag](prev: RDD[T]) extends RDD[(T, Long)](prev) {
/** The start index of each partition. */
@transient private val startIndices: Array[Long] = {
val n = prev.partitions.length
if (n == 0) {
Array.empty
} else if (n == 1) {
Array(0L)
} else {
prev.context.runJob(
prev,
Utils.getIteratorSize _,
0 until n - 1 // do not need to count the last partition
).scanLeft(0L)(_ + _)
}
}
override def getPartitions: Array[Partition] = {
firstParent[T].partitions.map(x => new ZippedWithIndexRDDPartition(x, startIndices(x.index)))
}
override def getPreferredLocations(split: Partition): Seq[String] =
firstParent[T].preferredLocations(split.asInstanceOf[ZippedWithIndexRDDPartition].prev)
override def compute(splitIn: Partition, context: TaskContext): Iterator[(T, Long)] = {
val split = splitIn.asInstanceOf[ZippedWithIndexRDDPartition]
val parentIter = firstParent[T].iterator(split.prev, context)
Utils.getIteratorZipWithIndex(parentIter, split.startIndex)
}
}
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