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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 org.apache.spark.util.collection
import java.util.Comparator
import org.apache.spark.storage.BlockObjectWriter
/**
* A common interface for size-tracking collections of key-value pairs that
* - Have an associated partition for each key-value pair.
* - Support a memory-efficient sorted iterator
* - Support a WritablePartitionedIterator for writing the contents directly as bytes.
*/
private[spark] trait WritablePartitionedPairCollection[K, V] {
/**
* Insert a key-value pair with a partition into the collection
*/
def insert(partition: Int, key: K, value: V): Unit
/**
* Iterate through the data in order of partition ID and then the given comparator. This may
* destroy the underlying collection.
*/
def partitionedDestructiveSortedIterator(keyComparator: Option[Comparator[K]])
: Iterator[((Int, K), V)]
/**
* Iterate through the data and write out the elements instead of returning them. Records are
* returned in order of their partition ID and then the given comparator.
* This may destroy the underlying collection.
*/
def destructiveSortedWritablePartitionedIterator(keyComparator: Option[Comparator[K]])
: WritablePartitionedIterator = {
val it = partitionedDestructiveSortedIterator(keyComparator)
new WritablePartitionedIterator {
private[this] var cur = if (it.hasNext) it.next() else null
def writeNext(writer: BlockObjectWriter): Unit = {
writer.write(cur._1._2, cur._2)
cur = if (it.hasNext) it.next() else null
}
def hasNext(): Boolean = cur != null
def nextPartition(): Int = cur._1._1
}
}
}
private[spark] object WritablePartitionedPairCollection {
/**
* A comparator for (Int, K) pairs that orders them by only their partition ID.
*/
def partitionComparator[K]: Comparator[(Int, K)] = new Comparator[(Int, K)] {
override def compare(a: (Int, K), b: (Int, K)): Int = {
a._1 - b._1
}
}
/**
* A comparator for (Int, K) pairs that orders them both by their partition ID and a key ordering.
*/
def partitionKeyComparator[K](keyComparator: Comparator[K]): Comparator[(Int, K)] = {
new Comparator[(Int, K)] {
override def compare(a: (Int, K), b: (Int, K)): Int = {
val partitionDiff = a._1 - b._1
if (partitionDiff != 0) {
partitionDiff
} else {
keyComparator.compare(a._2, b._2)
}
}
}
}
}
/**
* Iterator that writes elements to a BlockObjectWriter instead of returning them. Each element
* has an associated partition.
*/
private[spark] trait WritablePartitionedIterator {
def writeNext(writer: BlockObjectWriter): Unit
def hasNext(): Boolean
def nextPartition(): Int
}
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