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/*
* 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 spark
/**
* Base class for dependencies.
*/
abstract class Dependency[T](val rdd: RDD[T]) extends Serializable
/**
* Base class for dependencies where each partition of the parent RDD is used by at most one
* partition of the child RDD. Narrow dependencies allow for pipelined execution.
*/
abstract class NarrowDependency[T](rdd: RDD[T]) extends Dependency(rdd) {
/**
* Get the parent partitions for a child partition.
* @param partitionId a partition of the child RDD
* @return the partitions of the parent RDD that the child partition depends upon
*/
def getParents(partitionId: Int): Seq[Int]
}
/**
* Represents a dependency on the output of a shuffle stage.
* @param rdd the parent RDD
* @param partitioner partitioner used to partition the shuffle output
* @param serializerClass class name of the serializer to use
*/
class ShuffleDependency[K, V](
@transient rdd: RDD[_ <: Product2[K, V]],
val partitioner: Partitioner,
val serializerClass: String = null)
extends Dependency(rdd.asInstanceOf[RDD[Product2[K, V]]]) {
val shuffleId: Int = rdd.context.newShuffleId()
}
/**
* Represents a one-to-one dependency between partitions of the parent and child RDDs.
*/
class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
override def getParents(partitionId: Int) = List(partitionId)
}
/**
* Represents a one-to-one dependency between ranges of partitions in the parent and child RDDs.
* @param rdd the parent RDD
* @param inStart the start of the range in the parent RDD
* @param outStart the start of the range in the child RDD
* @param length the length of the range
*/
class RangeDependency[T](rdd: RDD[T], inStart: Int, outStart: Int, length: Int)
extends NarrowDependency[T](rdd) {
override def getParents(partitionId: Int) = {
if (partitionId >= outStart && partitionId < outStart + length) {
List(partitionId - outStart + inStart)
} else {
Nil
}
}
}
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