August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めての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.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.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.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.
56
4 章 キー／値ペアの処理
並列処理のレベルのチューニング
ここまでは、変換の処理はすべて分散処理されるということは述べてきましたが、実際に
Spark
がどのように処理を分割するかは、まだ見ていませんでした。すべての
RDD
は、決まった数の
ーを持っており、その数によって、
RDD
に対する処理を実行する際の並列度が決ま
ります。
集計やグループ化の処理を行う場合、
Spark
に対して特定の数のパーティションを使用するよう
要求できます。
Spark
は、クラスタのサイズに基づいて常に妥当なデフォルト値を推定しようとし
ますが、場合によってはパフォーマンスを向上させるために並列処理のレベルをチューニングした
い場合もあります。
本章で議論した操作のほとんどは、グループ化された
RDD
や集計結果の
RDD
を生成する際に
使用するパーティション数を指定する、第
2
のパラメータを受け付けます。
4-15
と
4-16
を参照してください。
4-15
ム
Python
reduceByKey()
data = [("a", 3), ("b", 4), ("a", 1)]
sc.parallelize(data).reduceByKey(lambda x, y: x + y) #
デフォルトの並列度
sc.parallelize(data).reduceByKey(lambda x, y: x + y, 10) #
カスタムの並列度
4-16
ム
Scala ...
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and much more.
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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.