spark MapPartitionsRDD 源码
spark MapPartitionsRDD 代码
文件路径：/core/src/main/scala/org/apache/spark/rdd/MapPartitionsRDD.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}
/**
* An RDD that applies the provided function to every partition of the parent RDD.
*
* @param prev the parent RDD.
* @param f The function used to map a tuple of (TaskContext, partition index, input iterator) to
* an output iterator.
* @param preservesPartitioning Whether the input function preserves the partitioner, which should
* be `false` unless `prev` is a pair RDD and the input function
* doesn't modify the keys.
* @param isFromBarrier Indicates whether this RDD is transformed from an RDDBarrier, a stage
* containing at least one RDDBarrier shall be turned into a barrier stage.
* @param isOrderSensitive whether or not the function is order-sensitive. If it's order
* sensitive, it may return totally different result when the input order
* is changed. Mostly stateful functions are order-sensitive.
*/
private[spark] class MapPartitionsRDD[U: ClassTag, T: ClassTag](
var prev: RDD[T],
f: (TaskContext, Int, Iterator[T]) => Iterator[U], // (TaskContext, partition index, iterator)
preservesPartitioning: Boolean = false,
isFromBarrier: Boolean = false,
isOrderSensitive: Boolean = false)
extends RDD[U](prev) {
override val partitioner = if (preservesPartitioning) firstParent[T].partitioner else None
override def getPartitions: Array[Partition] = firstParent[T].partitions
override def compute(split: Partition, context: TaskContext): Iterator[U] =
f(context, split.index, firstParent[T].iterator(split, context))
override def clearDependencies(): Unit = {
super.clearDependencies()
prev = null
}
@transient protected lazy override val isBarrier_ : Boolean =
isFromBarrier || dependencies.exists(_.rdd.isBarrier())
override protected def getOutputDeterministicLevel = {
if (isOrderSensitive && prev.outputDeterministicLevel == DeterministicLevel.UNORDERED) {
DeterministicLevel.INDETERMINATE
} else {
super.getOutputDeterministicLevel
}
}
}
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