August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
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83
5.2 ファイルフォーマット
たい場合には、そのデータに対して
map
を行い、保存前に変換をしておきます。先ほどの例（人々
と見たパンダの数）でロードしたデータの書き出しを考えてみましょう。
5-23
をご覧くだ
さい。
5-23
Scala
SequenceFile
ー
val data = sc.parallelize(List(("Panda", 3), ("Kay", 6), ("Snail", 2)))
data.saveAsSequenceFile(outputFile)
Java
の場合、
SequenceFile
のセーブにはもう少し手がかかります。これは、
JavaPairRDD
に
saveAsSequencefile
メソッドがないためであり、その代わりに
Hadoop
のカスタムフォーマット
に保存する機能を利用します。
Java
での
SequenceFile
への保存の方法は、「
5.2.6 Hadoop
の入出
力フォーマット」で紹介します。
5.2.5
ジクトフイル
オブジェクトファイルは、その名とは異なり、
SequenceFile
の単純なラッパーであり、値だけ
を含む
RDD
をセーブすることができます。
SequenceFile
の場合とは異なり、オブジェクトファ
イルでは
Java
のシリアライゼーションを使って値が書き出されます。
例えばフィールドの追加や削除を行い、クラスを変更した場合、古いオブジェクトファイルは読
めなくなってしまうかもしれません。オブジェクトファイルが使っている ...
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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.
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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.