August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
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64
4 章 キー／値ペアの処理
Java と Python におけるパーティショニング
Scala の API と同様に、Spark の Java および Python の API もパーティショニングによる恩恵
を被ります。ただし、Python では
partitionBy()
に
Hashpartitioner
オブジェクトを渡すことは
できません。その代わりに、単純に希望するパーティション数を渡すことができます（例えば
rdd.
partitionBy(100)
）。
4.5.1
RDD
のーテの
Scala
と
Java
では、
partitioner
プロパティを使って
RDD
のパーティショニングの方法を
指定できます
†
。このプロパティは
scala.Option
オブジェクトです。これは
Scala
のコンテナ
クラスで、アイテムを
1
つ含むか、まったく含んでいないかのどちらかです。この
Option
の
isDefined()
を呼べば値が設定されているかどうかを調べることができ、
get()
で値を得ることが
できます。値がある場合には、その値は
spark.Partitioner
オブジェクトです。基本的には、この
オブジェクトは
RDD
に対して、それぞれのキーの行き先のパーティションを知らせるものです。
このことについては、後ほど詳しく述べます。
partitioner
プロパティは、
Spark
の操作がどのようにパーティショニングに影響するのか、そ
してプログラム中で行いたい操作が適切な結果を生むことになるかを、
Spark
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.