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.
74
5 章 データのロードとセーブ
SparkContext.wholeTextFiles()
メソッドを使い、入力ファイルの名前をキーとするペア
RDD
を
得ることができます。
wholeTextFiles()
は、それぞれのファイルが一定期間のデータになっている場合にとても便利
です。それぞれのファイルに、異なる期間の販売データが入っているとすれば、それぞれの期間の
平均値は、
5-4
のようにすれば簡単に計算できます。
5-4
Scala
val input = sc.wholeTextFiles("file:///home/holden/salesFiles")
val result = input.mapValues{y =>
val nums = y.split(" ").map(x => x.toDouble)
nums.sum / nums.size.toDouble
}
Spark では、指定されたディレクトリ内のすべてのファイルの読み込みをサポートしており、その
際にワイルドカードの展開を行うことができます（例えば
part-*.txt
など）。大規模なデータセッ
トは複数のファイルにまたがっていることが多いので、特に他のファイル（処理の成功を示すマー
カーなど）が同じディレクトリにあるかもしれないような場合に、この機能が役立ちます。
テキストファイルの保存
テキストファイルの出力も、きわめてシンプルです。
5-5
の
saveAsTextFile()
メソッ ...
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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.